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{{Short description|Category of chemical elements}}
{{About|the chemical elements that are not metals|other meanings |Nonmetal (disambiguation)}}

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{| style="float:right; margin-left:2.5em; margin-bottom:1.2em; font-size:95%; max-width: 450px; border:1px solid grey"
| style=text-align:center|A [[periodic table]] extract {{nowrap|highlighting nonmetals}}
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| [[File:Nonmetals in the periodic table.png|450px| alt=A grid with 7 rows labeled periods "1" to "7" and 10 columns labeled as groups "1", "2", "3–11", and "12" to "18".
¶ Most cells represent one chemical element and are labeled with its 1 or 2 letter symbol in a large font above its name. Cells in column 3 (labeled "3–11") represent a series of elements and are labeled with the first and last element's symbol. 
¶ Row 1 has cells in the first and last columns, with an empty gap between. Rows 2–3 have 8 cells, with a gap between the first 2 and last 6 columns. Rows 4–7 have cells in all 10 columns. 
¶ A bold falling staircase line separates the rightmost 6/5/4/3/2/1 cells in rows 2–7.
¶ 17 cells above and right of the staircase are tan-colored: both cells row 1 and all cells to its right except the first one.
¶ 9 cells along the staircase are specially colored: gray in rows 2–5 and brown in rows 6-7: the first cell after it in rows 2–7 and first cell before in rows 4/5/7.
¶ The rest of the cells have light gray letters on a white background.]]
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}}always/usually considered nonmetals<ref name="Larrañaga"/><ref name="Steudel"/><ref name="Vernon2013"/>
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}}metalloids, sometimes considered nonmetals
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}}status as nonmetal or metal unconfirmed<ref>At: [[#Restrepo|Restrepo et al. 2006, p. 411]]; [[#Thornton|Thornton & Burdette 2010, p. 86]]; [[#Hermann|Hermann, Hoffmann & Ashcroft 2013, pp. 11604‒1‒11604‒5]]; <!--Cn: [[#Mewes|Mewes et al. 2019]]; Fl: [[#Florez|Florez et al. 2022]]; -->Ts: {{citation needed|date=April 2025}} Og: [[#Smits|Smits et al. 2020]]</ref>
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{{Sidebar periodic table}}
In the context of the periodic table, a '''nonmetal''' is a [[chemical element]] that mostly lacks distinctive [[metal]]lic properties. They range from colorless gases like [[hydrogen]] to shiny crystals like [[iodine]]. Physically, they are usually lighter (less dense) than elements that form metals and are often poor conductors of [[Thermal conduction|heat]] and [[Electrical conductor|electricity]]. Chemically, nonmetals have relatively high [[electronegativity]] or usually attract electrons in a chemical bond with another element, and their oxides tend to be [[acidic]].

Seventeen elements are widely recognized as nonmetals. Additionally, some or all of six borderline elements ([[metalloids]]) are sometimes counted as nonmetals.

The two lightest nonmetals, hydrogen and [[helium]], together account for about 98% of the mass of the [[observable universe]]. Five nonmetallic elements—hydrogen, carbon, [[nitrogen]], [[oxygen]], and [[silicon]]—form the bulk of Earth's [[Atmosphere of Earth|atmosphere]], [[biosphere]], [[Earth's crust|crust]] and [[ocean]]s, although metallic elements are believed to be slightly more than half of the overall composition of the Earth.

[[Chemical compound]]s and [[alloys]] involving multiple elements including nonmetals are widespread. Industrial uses of nonmetals as the dominant component include in [[electronics]], [[combustion]], [[lubrication]] and [[machining]].

Most nonmetallic elements were identified in the 18th and 19th centuries. While a distinction between metals and other minerals had existed since antiquity, a classification of chemical elements as metallic or nonmetallic emerged only in the late 18th century. Since then about twenty properties have been suggested as criteria for distinguishing nonmetals from metals. In contemporary research usage it is common to use a [[Nonmetal#Structure, quantum mechanics and band structure|distinction between metal and not-a-metal]] based upon the electronic structure of the solids; the elements carbon, arsenic and antimony are then [[semimetal]]s, a subclass of metals. The rest of the nonmetallic elements are insulators, some of which such as silicon and germanium can readily accommodate [[Doping (semiconductor)|dopants]] that change the electrical conductivity leading to [[semiconducting]] behavior.

==Definition and applicable elements==
:''Unless otherwise noted, this article describes the stable form of an element at [[standard temperature and pressure]] (STP).''{{efn|The most stable forms are: diatomic [[hydrogen]] H<sub>2</sub>; [[allotropes of boron#β-rhombohedral boron|β-rhombohedral boron]]; [[graphite]] for [[carbon]]; diatomic [[nitrogen]] N<sub>2</sub>; diatomic [[oxygen]] O<sub>2</sub>; tetrahedral [[silicon]]; [[black phosphorus]]; orthorhombic [[sulfur]] S<sub>8</sub>; [[germanium#Characteristics|α-germanium]]; gray [[arsenic]]; gray [[selenium]]; gray [[antimony]]; gray [[tellurium]]; and diatomic [[iodine]] I<sub>2</sub>. All other nonmetallic elements have only one stable form at [[standard temperature and pressure|STP]].<ref>[[#Wismer|Wismer 1997, p. 72]]: H, He, C, N, O, F, Ne, S, Cl, Ar, As, Se, Br, Kr, Sb, I, Xe; [[#Powell|Powell 1974, pp. 174, 182]]: P, Te; [[#Greenwood|Greenwood & Earnshaw 2002, p. 143]]: B; [[#Field|Field 1979, p. 403]]: Si, Ge; [[#Addison|Addison 1964, p. 120]]: Rn</ref>}}
[[File:Arsen 1a.jpg|thumb|While [[arsenic]] (here sealed in a container to prevent [[tarnishing]]) has a shiny appearance and is a reasonable conductor of heat and electricity, it is soft and brittle and its chemistry is predominately nonmetallic.<ref>[[#Pascoe|Pascoe 1982, p. 3]]</ref>|alt=Two dull silver clusters of crystalline shards.]]

Nonmetallic [[chemical elements]] are often broadly defined as those that mostly lack properties commonly associated with metals—namely shininess, pliability, good thermal and electrical conductivity (due to their  [[Nonmetal#Structure, quantum mechanics and band structure|band structure]]), and a general capacity to form basic oxides.<ref>[[#MD|Malone & Dolter 2010, pp. 110–111]]</ref><ref name="Porterfield"/> There is no widely accepted precise definition in terms of these properties;<ref>[[#Godovikov|Godovikov & Nenasheva 2020, p. 4]]; [[#Morley|Morely & Muir 1892, p. 241]]</ref> any list of nonmetals is open to debate and revision.<ref name="Larrañaga">[[#Larrañaga|Larrañaga, Lewis & Lewis 2016, p. 988]]</ref>

Fourteen elements are almost always recognized as nonmetals:<ref name="Larrañaga"/><ref name="Steudel">[[#Steudel|Steudel 2020, p. 43]]: Steudel's monograph is an updated translation of the fifth German edition of 2013, incorporating the literature up to Spring 2019.</ref>
{{hlist | indent=1 | [[Hydrogen]] | [[Nitrogen]] | [[Oxygen]] | [[Sulfur]] }}
{{hlist | indent=1 | [[Fluorine]] | [[Chlorine]] | [[Bromine]] | [[Iodine]] }}
{{hlist | indent=1 | [[Helium]] | [[Neon]] | [[Argon]] | [[Krypton]] | [[Xenon]] | [[Radon]] }}

Three more are commonly classed as nonmetals, but some sources list them as "[[metalloids]]",<ref name="Vernon2013">[[#Vernon2013|Vernon 2013]]</ref> a term which refers to elements intermediate between metals and nonmetals:<ref name="Vernon2020p220">[[#Vernon2020|Vernon 2020, p. 220]]; [[#Rochow1966|Rochow 1966, p. 4]]</ref>
{{hlist | indent=1 | [[Carbon]] | [[Phosphorus]] | [[Selenium]] }}

One or more of the six elements most commonly recognized as metalloids are sometimes instead counted as nonmetals: 
{{hlist | indent=1 | [[Boron]] | [[Silicon]] | [[Germanium]] | [[Arsenic]] | [[Antimony]] | [[Tellurium]] }}

About 15–20% of the 118 known elements<ref>[[#IUPACPT|IUPAC Periodic Table of the Elements]]</ref> are thus classified as nonmetals.{{efn|At higher temperatures and pressures the numbers of nonmetals can be called into question. For example, when germanium melts it changes from a semiconductor to a metallic conductor with an electrical conductivity similar to that of liquid mercury.<ref>[[#Berger1997|Berger 1997, pp.&nbsp;71–72]]</ref> At a high enough pressure, [[sodium]] (a metal) becomes a non-conducting [[insulator (electricity)|insulator]].<ref>[[#Gatti|Gatti, Tokatly & Rubio 2010]]</ref>}}

==General properties==
===Physical===
{{hatnote|See also {{slink||Physical properties by element type}}}}

{{multiple image|perrow=3|total_width=330|caption_align=center
| align = right
| image_style = border:none;
|image1=Boron R105.jpg
 |alt1=Several dozen small angular stone like shapes, grey with scattered silver flecks and highlights.
 |caption1= Boron in its β-[[rhombohedral]] phase
|image2=Graphite2.jpg
 |alt2=A shiny grey-black cuboid nugget with a rough surface.
 |caption2= Metallic appearance of [[carbon]] as [[graphite]]
|image3=Liquid oxygen in a beaker 4.jpg
 |alt3=A pale blue liquid in a clear beaker
 |caption3= Blue color of [[liquid oxygen]]
|image4=Liquid fluorine tighter crop.jpg
 |alt4=A glass tube, is inside a larger glass tube, has some clear yellow liquid in it
 |caption4= Pale yellow liquid fluorine in a [[cryogenics|cryogenic bath]]
|image5=Sulfur-sample.jpg
 |alt5=Yellow powdery chunks
 |caption5= [[Sulfur]] as yellow chunks
|image6=Bromine_in_a_vial.png
 |alt6=A small capped jar a quarter filled with a very dark liquid
 |caption6= Liquid [[bromine]] at room temperature
|image7=Iodinecrystals.JPG
 |caption7= Metallic appearance of [[iodine]] under white light
 |alt7=Shiny violet-black colored crystalline shards.
|image8=An acrylic cube specially prepared for element collectors containing an ampoule filled with liquefied xenon.JPG
 |alt8=A partly filled ampoule containing a colorless liquid
 |caption8= Liquefied xenon
| header = {{font|size=100%|font=Sans-serif|text=Variety in color and form<br />of some nonmetallic elements}}
}}

Nonmetals vary greatly in appearance, being colorless, colored or shiny.<!-- It would be nice to say "due to the structure of their electrons" or something like that, as is mentioned w/r/t shiny solids and colorless gases, but nothing is stated about the electronics of the colored ones -->
For the colorless nonmetals (hydrogen, nitrogen, oxygen, and the noble gases), no absorption of light happens in the visible part of the spectrum, and all visible light is transmitted.<ref>[[#Wibaut|Wibaut 1951, p. 33]]: "Many substances&nbsp;...are colourless and therefore show no selective absorption in the visible part of the spectrum."</ref>
The colored nonmetals (sulfur, fluorine, chlorine, bromine) absorb some colors (wavelengths) and transmit the complementary or opposite colors. For example, chlorine's "familiar yellow-green colour&nbsp;... is due to a broad region of absorption in the violet and blue regions of the spectrum".<ref>[[#Elliot|Elliot 1929, p. 629]]</ref>{{efn|The absorbed light may be converted to heat or re-emitted in all directions so that the emission spectrum is thousands of times weaker than the incident light radiation.<ref>[[#Fox|Fox 2010, p. 31]]</ref>}} The shininess of boron, graphite (carbon), silicon, black phosphorus, germanium, arsenic, selenium, antimony, tellurium, and iodine{{efn|Solid iodine has a silvery metallic appearance under white light at room temperature. At ordinary and higher temperatures it [[sublimation (phase transition)|sublimes]] from the solid phase directly into a violet-colored vapor.<ref>[[#Tidy|Tidy 1887, pp. 107–108]]; [[#Koenig|Koenig 1962, p. 108]]</ref>}} is a result of the electrons reflecting incoming visible light.<ref>[[#Wiberg|Wiberg 2001, p. 416]]; Wiberg is here referring to iodine.</ref>

About half of nonmetallic elements are gases under [[standard temperature and pressure]]; most of the rest are solids. Bromine, the only liquid, is usually topped by a layer of its reddish-brown fumes. The gaseous and liquid nonmetals have very low densities, [[melting point|melting]] and [[boiling point]]s, and are poor conductors of heat and electricity.<ref name="Kneen">[[#Kneen|Kneen, Rogers & Simpson 1972, pp. 261–264]]</ref> The solid nonmetals have low densities and low mechanical strength (being either hard and brittle, or soft and crumbly),<ref name="ReferenceA">[[#Johnson1966|Johnson 1966, p. 4]]</ref> and a wide range of electrical conductivity.{{efn|The solid nonmetals have electrical conductivity values ranging from 10<sup>−18</sup> S•cm<sup>−1</sup> for sulfur<ref name="A&W"/> to 3 × 10<sup>4</sup> in graphite<ref name="Jenkins">[[#Jenkins|Jenkins & Kawamura 1976, p. 88]]</ref> or 3.9 × 10<sup>4</sup> for [[arsenic]];<ref>[[#Carapella|Carapella 1968, p. 30]]</ref> cf. 0.69 × 10<sup>4</sup> for [[manganese]] to 63 × 10<sup>4</sup> for [[silver]], both metals.<ref name="A&W">[[#Aylward|Aylward & Findlay 2008, pp. 6–12]]</ref> The conductivity of graphite and arsenic (both semimetals) exceed that of manganese.}}

This diversity stems from variability in crystallographic structures and bonding arrangements. Covalent nonmetals existing as discrete atoms like xenon, or as small molecules, such as oxygen, sulfur, and bromine, have low melting and boiling points; many are gases at room temperature, as they are held together by weak [[London dispersion force]]s acting between their atoms or molecules, although the molecules themselves have strong covalent bonds.<ref>[[#ZumDeC|Zumdahl & DeCoste 2010, pp. 455, 456, 469, A40]]; [[#Earl&W|Earl & Wilford 2021, p. 3-24]]</ref> In contrast, nonmetals that form extended structures, such as long chains of selenium atoms,<ref>{{Cite journal |last1=Corb |first1=B.W. |last2=Wei |first2=W.D. |last3=Averbach |first3=B.L. |date=1982 |title=Atomic models of amorphous selenium |url=https://linkinghub.elsevier.com/retrieve/pii/0022309382900163 |journal=Journal of Non-Crystalline Solids |language=en |volume=53 |issue=1–2 |pages=29–42 |doi=10.1016/0022-3093(82)90016-3|bibcode=1982JNCS...53...29C |url-access=subscription }}</ref> sheets of carbon atoms in graphite,<ref>[[#Wiberg|Wiberg 2001, pp. 780]]</ref> or three-dimensional lattices of silicon atoms<ref>[[#Wiberg|Wiberg 2001, pp. 824, 785]]</ref> have higher melting and boiling points, and are all solids. Nonmetals closer to the left or bottom of the periodic table (and so closer to the metals) often have [[Metallic bonding|metallic interactions]] between their molecules, chains, or layers; this occurs in boron,<ref>[[#Siekierski|Siekierski & Burgess 2002, p. 86]]</ref> carbon,<ref>[[#Charlier|Charlier, Gonze & Michenaud 1994]]</ref> phosphorus,<ref>[[#Taniguchi|Taniguchi et al. 1984, p. 867]]: "...&nbsp;black phosphorus&nbsp;... [is] characterized by the wide valence bands with rather delocalized nature."; [[#Carmalt|Carmalt & Norman 1998, p. 7]]: "Phosphorus&nbsp;... should therefore be expected to have some metalloid properties."; [[#Du|Du et al. 2010]]: Interlayer interactions in black phosphorus, which are attributed to van der Waals-Keesom forces, are thought to contribute to the smaller band gap of the bulk material (calculated 0.19&nbsp;eV; observed 0.3&nbsp;eV) as opposed to the larger band gap of a single layer (calculated ~0.75&nbsp;eV).</ref> arsenic,<ref>[[#Wiberg|Wiberg 2001, pp. 742]]</ref> selenium,<ref>[[#Evans|Evans 1966, pp. 124–25]]</ref> antimony,<ref>[[#Wiberg|Wiberg 2001, pp. 758]]</ref> tellurium<ref>[[#Stuke|Stuke 1974, p. 178]]; [[#Donohue|Donohue 1982, pp. 386–87]]; [[#Cotton|Cotton et al. 1999, p. 501]]</ref> and iodine.<ref>[[#Steudel|Steudel 2020, p. 601]]: "...&nbsp;Considerable orbital overlap can be expected. Apparently, intermolecular multicenter bonds exist in crystalline iodine that extend throughout the layer and lead to the delocalization of electrons akin to that in metals. This explains certain physical properties of iodine: the dark color, the luster and a weak electric conductivity, which is 3400 times stronger within the layers then perpendicular to them. Crystalline iodine is thus a two-dimensional semiconductor."; [[#Segal|Segal 1989, p. 481]]: "Iodine exhibits some metallic properties&nbsp;..."</ref>

{|class="wikitable floatright" style="line-height: 1.3; font-size: 95%; margin-left:20px; margin-bottom:1.2em"
|+ Some general physical differences<br />between elemental metals and nonmetals<ref name="Kneen"/>
|-
! Aspect !! Metals !! Nonmetals
|-
|Appearance<br />and form
|Shiny if freshly prepared<br />or fractured; few colored;<ref>[[#Taylor|Taylor 1960, p. 207]]; [[#Brannt|Brannt 1919, p. 34]]</ref><br />all but one solid<ref name="Green">[[#Green|Green 2012, p. 14]]</ref>
|Shiny, colored or<br />transparent;<ref>[[#Spencer|Spencer, Bodner & Rickard 2012, p. 178]]</ref> all but<br />one solid or gaseous<ref name="Green"/>
|-
|[[Density]]
| Often higher
| Often lower
|-
| [[Plasticity (physics)|Plasticity]]
| Mostly malleable<br />and ductile
| Often brittle solids
|-
| [[Electrical conductivity|Electrical]]<br />[[Electrical conductivity|conductivity]]<ref>[[#Redmer|Redmer, Hensel & Holst 2010, preface]]</ref>
| Good
| Poor to good
|-
| [[Electronic band structure|Electronic]]<br />[[Electronic band structure|structure]]<ref name="K&W"/>
| Metal or [[semimetal]]ic
| Semimetal,<br />[[semiconductor]],<br />or [[insulator (electricity)|insulator]]
|}
Covalently bonded nonmetals often share only the electrons required to achieve a noble gas electron configuration.<ref>[[#DeKock|DeKock & Gray 1989, pp. 423, 426—427]]</ref> For example, nitrogen forms diatomic molecules featuring a triple bonds between each atom, both of which thereby attain the configuration of the noble gas neon. In contrast antimony has buckled layers in which each antimony atom is singly bonded with three other nearby atoms.<ref>[[#Boreskov|Boreskov 2003, p. 45]]</ref>

Good electrical conductivity occurs when there is [[metallic bond]]ing,<ref name="Ashcroft and Mermin">[[Ashcroft and Mermin]]</ref> however the electrons in some nonmetals are not metallic.<ref name="Ashcroft and Mermin"/> Good electrical and thermal conductivity associated with metallic electrons is seen in carbon (as graphite, along its planes), arsenic, and antimony.{{efn|Thermal conductivity values for metals range from 6.3 W m<sup>−1</sup> K<sup>−1</sup> for [[neptunium]] to 429 for [[silver]]; cf. antimony 24.3, arsenic 50, and carbon 2000.<ref name="A&W"/> Electrical conductivity values of metals range from 0.69 S•cm<sup>−1</sup> × 10<sup>4</sup> for [[manganese]] to 63 × 10<sup>4</sup> for [[silver]]; cf. carbon 3 × 10<sup>4</sup>,<ref name="Jenkins"/> arsenic 3.9 × 10<sup>4</sup> and antimony 2.3 × 10<sup>4</sup>.<ref name="A&W"/>}} Good thermal conductivity occurs in boron, silicon, phosphorus, and germanium;<ref name="A&W"/> such conductivity is transmitted though vibrations of the crystalline lattices ([[phonons]] of these elements.<ref>[[#Yang|Yang 2004, p. 9]]</ref> Moderate electrical conductivity is observed in the semiconductors<ref>[[#Wiberg|Wiberg 2001, pp. 416, 574, 681, 824, 895, 930]]; [[#Siekierski|Siekierski & Burgess 2002, p. 129]]</ref> boron, silicon, phosphorus, germanium, selenium, tellurium, and iodine.

Many of the nonmetallic elements are hard and brittle,<ref name="ReferenceA"/> where [[dislocations]] cannot readily move so they tend to undergo [[brittle fracture]] rather than deforming.<ref>{{Cite book |last1=Weertman |first1=Johannes |title=Elementary dislocation theory |last2=Weertman |first2=Julia R. |date=1992 |publisher=Oxford University Press |isbn=978-0-19-506900-6 |location=New York}}</ref> Some do deform such as [[allotropes of phosphorus#White phosphorus|white phosphorus]] (soft as wax, pliable and can be cut with a knife at room temperature),<ref name="Holderness 1979, p. 255">[[#Faraday|Faraday 1853, p. 42]]; [[#Holderness|Holderness & Berry 1979, p. 255]]</ref> [[allotropes of sulfur#Amorphous sulfur|plastic sulfur]],<ref name="ReferenceE">[[#Partington1944|Partington 1944, p. 405]]</ref> and selenium which can be drawn into wires from its molten state.<ref name="ReferenceF">[[#Regnault|Regnault 1853, p. 208]]</ref> Graphite is a standard [[solid lubricant]] where dislocations move very easily in the basal planes.<ref name=":1">{{Cite journal |last1=Scharf |first1=T. W. |last2=Prasad |first2=S. V. |date=January 2013 |title=Solid lubricants: a review |url=http://link.springer.com/10.1007/s10853-012-7038-2 |journal=Journal of Materials Science |language=en |volume=48 |issue=2 |pages=511–531 |doi=10.1007/s10853-012-7038-2 |bibcode=2013JMatS..48..511S |issn=0022-2461|url-access=subscription }}</ref>

====Allotropes====
{{multiple image
| perrow            = 3
| total_width       = 350
| align             = right
| image_style       = border:none;
| image1            = Diamond-dimd15a.jpg
| alt1              = A clear triangular crystal with a flat face and slightly rough edges
| caption1          = A transparent electrical{{nbsp}}insulator
| image2            = C60-Fulleren-kristallin (cropped).JPG
| alt2              = a haphazard aggregate of brownish crystals
| caption2          = A brownish semiconductor
| image3            = Graphite-233436.jpg
| alt3              = A black multi-layered lozenge-shaped rock
| caption3          = A blackish semimetal
| header            = Three allotropes of carbon
| footer            = From left to right, [[diamond]], [[buckminsterfullerene]], and [[graphite]]
| caption_align     = center
| footer_align      = center
}}
{{Main list|Allotropy#Non-metals|Single-layer materials}}
Over half of the nonmetallic elements exhibit a range of less stable allotropic forms, each with distinct physical properties.<ref>[[#Barton|Barton 2021, p. 200]]</ref> For example, carbon, the most stable form of which is [[graphite]], can manifest as [[diamond]], [[buckminsterfullerene]],<ref>[[#Wiberg|Wiberg 2001, p. 796]]</ref> [[amorphous]]<ref>[[#Shang|Shang et al. 2021]]</ref> and [[Paracrystallinity|paracrystalline]]<ref>[[#Tang|Tang et al. 2021]]</ref> variations. Allotropes also occur for nitrogen, oxygen, phosphorus, sulfur, selenium and iodine.<ref>[[#Steudel|Steudel 2020, ''passim'']]; [[#Carrasco|Carrasco et al. 2023]]; [[#Shanabrook|Shanabrook, Lannin & Hisatsune 1981, pp. 130–133]]</ref>

===Chemical===
{{hatnote|See also {{slink||Chemical properties by element type}}}}
{|class="wikitable floatright" style="line-height: 1.3; font-size: 95%; margin-left:20px"
|+ Some general chemistry-based<br/>differences between metals and nonmetals<ref name="Kneen"/>
|-
! colspan=2 | Aspect !! Metals !! Nonmetals
|-
| colspan=2 |Reactivity<ref>[[#Weller|Weller et al. 2018, preface]]</ref>
| colspan=2 style="text-align: center"| Wide range: very reactive to noble
|-
| rowspan =2 | [[Oxide]]s || lower
| [[base (chemistry)|Basic]]
| rowspan =2 | [[Acid]]ic; never basic<ref name="ReferenceC">[[#Abbott|Abbott 1966, p. 18]]</ref>
|-
| higher || Increasingly acidic
|-
| colspan=2 |Compounds<br />with metals<ref>[[#Ganguly|Ganguly 2012, p. 1-1]]</ref>
| [[Alloy]]s
| [[Covalent bond|Covalent]] or [[Ionic compounds|Ionic]]
|-
| colspan=2 | [[Ionization energy]]<ref name="AylwardIE"/>
| Low to high
| Moderate to very high
|-
| colspan=2 | [[Electronegativity]]<ref name="AylwardEN"/>
| Low to high
| Moderate to very high
|}
Nonmetals have relatively high values of electronegativity, and their oxides are usually acidic. Exceptions may occur if a nonmetal is not very electronegative, or if its [[oxidation state]] is low, or both. These non-acidic oxides of nonmetals may be [[amphoteric]] (like water, H<sub>2</sub>O<ref>[[#Eagleson1994|Eagleson 1994, 1169]]</ref>) or neutral (like [[nitrous oxide]], N<sub>2</sub>O<ref>[[#Moody|Moody 1991, p. 365]]</ref>{{efn|While [[carbon monoxide|CO]] and [[nitrogen monoxide|NO]] are commonly referred to as being neutral, CO is a slightly acidic oxide, reacting with bases to produce formates (CO + OH<sup>−</sup> → HCOO<sup>−</sup>);<ref>[[#House2013|House 2013, p. 427]]</ref> and in water, NO reacts with oxygen to form nitrous acid HNO<sub>2</sub> (4NO + O<sub>2</sub> + 2H<sub>2</sub>O → 4HNO<sub>2</sub>).<ref>[[#LewisRS|Lewis & Deen 1994, p. 568]]</ref>}}), but never basic.

They tend to gain electrons during chemical reactions, in contrast to metallic elements which tend to donate electrons. This behavior is related to the stability of [[electron configuration]]s in the noble gases, which have complete outer [[electron shell|shells]], empirically described by the [[Octet rule#Other rules|duet]] and [[octet rule]]s of thumb, more correctly explained in terms of [[valence bond theory]].<ref>[[#SmithDW|Smith 1990, pp. 177–189]]</ref>

The chemical differences between metals and nonmetals stem from variations in how strongly atoms attract and retain electrons. Across a period of the periodic table, the nuclear charge increases as more protons are added to the nucleus.<ref>[[#Young2018|Young et al. 2018, p. 753]]</ref> However, because the number of inner electron shells remains constant, the [[effective nuclear charge]] experienced by the outermost electrons also increases, pulling them closer to the nucleus. This leads to a corresponding reduction in atomic radius,<ref>[[#Brown et al.|Brown et al. 2014, p. 227]]</ref> and a greater tendency of these elements to gain electrons during chemical reactions, forming negatively charged ions.<ref>[[#Moore|Moore 2016]]; [[#Burford|Burford, Passmore & Sanders 1989, p. 54]]</ref> Nonmetals, which occupy the right-hand side of the periodic table, exemplify this behavior.

Nonmetals typically exhibit higher [[ionization energy|ionization energies]], [[electron affinity|electron affinities]], and [[standard electrode potential]]s than metals. The higher these values are (including electronegativity) the more nonmetallic the element tends to be.<ref>[[#Yoder|Yoder, Suydam & Snavely 1975, p. 58]]</ref> For example, the chemically very active nonmetals fluorine, chlorine, bromine, and iodine have an average electronegativity of 3.19—a figure{{efn|Electronegativity values of fluorine to iodine are: 3.98 + 3.16 + 2.96 + 2.66 &#61; 12.76/4 3.19.}} higher than that of any metallic element.

The number of compounds formed by nonmetals is vast.<ref>[[#Brady|Brady & Senese 2009, p. 69]]</ref> The first 10 places in a "top 20" table of elements most frequently encountered in 895,501,834 compounds, as listed in the [[Chemical Abstracts Service]] register for November 2, 2021, were occupied by nonmetals. Hydrogen, carbon, oxygen, and nitrogen collectively appeared in most (80%) of compounds. Silicon, a metalloid, ranked 11th. The highest-rated metal, with an occurrence frequency of 0.14%, was iron, in 12th place.<ref>[[#CAS|Chemical Abstracts Service 2021]]</ref>

===Complications===

Adding complexity to the chemistry of the nonmetals are anomalies occurring in the first row of each [[periodic table block]]; non-uniform periodic trends; higher oxidation states; multiple bond formation; and property overlaps with metals.

====First-row anomaly====
<div style="line-height:1px;">[[Image:1x1.png|link=|alt=A table with seven rows and ten columns. Rows are labeled on the left with a period number from 1 through 7. Columns are labeled on the bottom with a group number. Most cells represent a single chemical element and have two lines of information: the element's symbol on the top and its atomic number on the bottom. The table as a whole is divided into four rectangular areas separated from each other by narrow gaps. The first rectangle fills all seven rows of the first two columns. The rectangle is labeled "s-block" at the top and its two columns are labeled with group numbers "(1)" and "(2)" on the bottom. The cells in the first row - hydrogen and helium, with symbols H and He and atomic numbers 1 and 2 respectively - are both shaded red. The second rectangle fills the bottom two rows (periods 6 and 7) of the third column. Just above these cells is the label "f-block"; there is no group label on the bottom. The topmost cell - labeled "La-Yb" for elements 57-70 - is shaded green. The third rectangle fills the bottom four rows (periods 4 through 7) of the fourth column. Just above these cells is the label "d-block"; at the bottom is the label "(3-12)" for the group numbers of these elements. The topmost cell - labeled "Sc-Zn" for elements 21-30 - is shaded blue. The fourth and last rectangle fills the bottom six rows (periods 2 through 7) of the last six columns. Just above these cells is the label "p-block"; at the bottom are labels "(13)" through "(18) for the group numbers of these elements. The cells in the topmost row - for the elements boron (B,5), carbon (C,6), nitrogen (N,7), oxygen (O,8), fluorine (Fl,9), and neon (Ne,10) - are shaded yellow. Bold lines encircle the cells of the nonmetals - the top two cells on the left and 21 cells in the upper right of the table.]]</div>
{| class=" floatright" style="border-collapse:collapse; text-align:center;font-size:80%;line-height:1.1;margin-top:1.2em;"
| colspan=14 style="padding-bottom:3px;border:none;text-align:center;font-size:105%" | '''Condensed periodic table highlighting<br />the first row of each block: {{color box|{{element color|s-block}}|s}} {{color box|{{element color|p-block}}|p}} {{color box|{{element color|d-block}}|d}} and {{color box|{{element color|f-block}}|f}}'''
|-
| colspan=1 | '''Period'''
| colspan=2 | '''{{nowrap|s-block}}'''
| rowspan=9 style="padding:1px;" |
| colspan=1 |
| rowspan=9 style="padding:1px;" |
| colspan=1 |
| rowspan=9 style="padding:1px;" |
| colspan=6 |
|-
| '''1'''
| style="border:solid black;border-width:2px 1px 2px 2px;background-color:{{element color|s-block}};" | H <br />1
| style="border:solid black;border-width:2px 2px 2px 1px;background-color:{{element color|s-block}};" | He<br />2
| 
| 
| colspan=6 | <br />'''p-block'''
|-
| '''2'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Li<br />3
| style="border:solid black;border-width:1px 1px 1px 1px;" | Be<br />4
|
|
| style="border:solid black;border-width:2px 1px 2px 2px;background-color:{{element color|p-block}};" | B <br />5
| style="border:solid black;border-width:2px 1px 1px 1px;background-color:{{element color|p-block}};" | C <br />6
| style="border:solid black;border-width:2px 1px 1px 1px;background-color:{{element color|p-block}};" | N <br />7
| style="border:solid black;border-width:2px 1px 1px 1px;background-color:{{element color|p-block}};" | O <br />8
| style="border:solid black;border-width:2px 1px 1px 1px;background-color:{{element color|p-block}};" | F <br />9
| style="border:solid black;border-width:2px 2px 1px 1px;background-color:{{element color|p-block}};" | Ne<br />10
|-
| '''3'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Na<br />11
| style="border:solid black;border-width:1px 1px 1px 1px;" | Mg<br />12
|
| <br />'''{{nowrap|d-block}}'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Al<br />13
| style="border:solid black;border-width:1px 1px 1px 2px;" | Si<br />14
| style="border:solid black;border-width:1px 1px 1px 1px;" | P <br />15
| style="border:solid black;border-width:1px 1px 1px 1px;" | S <br />16
| style="border:solid black;border-width:1px 1px 1px 1px;" | Cl<br />17
| style="border:solid black;border-width:1px 2px 1px 1px;" | Ar<br />18
|-
| '''4'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | K <br />19
| style="border:solid black;border-width:1px 1px 1px 1px;" | Ca<br />20
|
| style="border:solid black;border-width:1px 1px 1px 1px;background-color:{{element color|d-block}};" | Sc-Zn<br />21-30
| style="border:solid black;border-width:1px 1px 1px 1px;" | Ga<br />31
| style="border:solid black;border-width:1px 1px 2px 2px;" | Ge<br />32
| style="border:solid black;border-width:1px 1px 1px 1px;" | As<br />33
| style="border:solid black;border-width:1px 1px 1px 1px;" | Se<br />34
| style="border:solid black;border-width:1px 1px 1px 1px;" | Br<br />35
| style="border:solid black;border-width:1px 2px 1px 1px;" | Kr<br />36
|-
| '''5'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Rb<br />37
| style="border:solid black;border-width:1px 1px 1px 1px;" | Sr<br />38
| <br />'''{{nowrap|f-block}}'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Y-Cd<br />39-48
| style="border:solid black;border-width:1px 1px 1px 1px;" | In<br />49
| style="border:solid black;border-width:1px 1px 1px 1px;" | Sn<br />50
| style="border:solid black;border-width:1px 1px 2px 2px;" | Sb<br />51
| style="border:solid black;border-width:1px 1px 2px 1px;" | Te<br />52
| style="border:solid black;border-width:1px 1px 2px 1px;" | I <br />53
| style="border:solid black;border-width:1px 2px 1px 1px;" | Xe<br />54
|-
| '''6'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Cs<br />55
| style="border:solid black;border-width:1px 1px 1px 1px;" | Ba<br />56
| style="border:solid black;border-width:1px 1px 1px 1px;background-color:{{element color|f-block}};" | La-Yb<br />57-70
| style="border:solid black;border-width:1px 1px 1px 1px;" | ''Lu-Hg<br />71-80''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Tl<br />81
| style="border:solid black;border-width:1px 1px 1px 1px;" | Pb<br />82
| style="border:solid black;border-width:1px 1px 1px 1px;" | Bi<br />83
| style="border:solid black;border-width:1px 1px 1px 1px;" | Po<br />84
| style="border:solid black;border-width:1px 1px 1px 1px;" | At<br />85
| style="border:solid black;border-width:1px 2px 2px 2px;" | Rn<br />86
|-
| '''7'''
| style="border:solid black;border-width:1px 1px 1px 1px;" | Fr<br />87
| style="border:solid black;border-width:1px 1px 1px 1px;" | Ra<br />88
| style="border:solid black;border-width:1px 1px 1px 1px;" | Ac-No<br />89-102
| style="border:solid black;border-width:1px 1px 1px 1px;" | Lr-Cn<br />103-112
| style="border:solid black;border-width:1px 1px 1px 1px;" | Nh<br />113
| style="border:solid black;border-width:1px 1px 1px 1px;" | Fl<br />114
| style="border:solid black;border-width:1px 1px 1px 1px;" | Mc<br />115
| style="border:solid black;border-width:1px 1px 1px 1px;" | Lv<br />116
| style="border:solid black;border-width:1px 1px 1px 1px;" | Ts<br />117
| style="border:solid black;border-width:1px 1px 1px 1px;" | Og<br />118
|-
| ''Group''
| ''(1)''
| ''(2)''
|
| ''(3-12)''
| ''(13)''
| ''(14)''
| ''(15)''
| ''(16)''
| ''(17)''
| ''(18)''
|-
| colspan=14 style="border:none;"|
|-
| colspan=14 style="border:none; text-align:Center;font-size:105%;"| The [[Kainosymmetry|first-row anomaly]] strength by block is '''s''' >> '''p''' > '''d''' > '''f'''.<ref>[[#Jensen|Jensen 1986, p. 506]]</ref>{{efn|Helium is shown above beryllium for electron configuration consistency purposes; as a noble gas it is usually placed above neon, in group 18.}}
|}
Starting with hydrogen, the [[Kainosymmetry|first-row anomaly]] primarily arises from the electron configurations of the elements concerned. Hydrogen is notable for its diverse bonding behaviors. It most commonly forms covalent bonds, but it can also lose its single electron in an [[aqueous solution]], leaving behind a bare proton with high polarizing power.<ref>[[#Lee|Lee 1996, p. 240]]</ref> Consequently, this proton can attach itself to the lone electron pair of an oxygen atom in a water molecule, laying the foundation for [[acid–base reaction|acid–base chemistry]].<ref>[[#Greenwood|Greenwood & Earnshaw 2002, p. 43]]</ref> Moreover, a hydrogen atom in a molecule can form a [[hydrogen bonding|second, albeit weaker, bond]] with an atom or group of atoms in another molecule. Such bonding, "helps give [[snowflake]]s their hexagonal symmetry, binds [[DNA]] into a [[double helix]]; shapes the three-dimensional forms of [[protein]]s; and even raises water's boiling point high enough to make a decent cup of tea."<ref>[[#Cressey|Cressey 2010]]</ref>

Hydrogen and helium, as well as boron through neon, have small atomic radii. The ionization energies and electronegativities among these elements are higher than the [[periodic trends]] would otherwise suggest.

While it would normally be expected, on electron configuration consistency grounds, that hydrogen and helium would be placed atop the s-block elements, the significant first-row anomaly shown by these two elements justifies alternative placements. Hydrogen is occasionally positioned above fluorine, in group 17, rather than above lithium in group 1. Helium is almost always placed above neon, in group 18, rather than above beryllium in group 2.<ref>[[#Petruševski|Petruševski & Cvetković 2018]]; [[#Grochala|Grochala 2018]]</ref>

====Secondary periodicity====
[[File:EN values of chalcogens.png|thumb|upright=0.8|Electronegativity values of the group 16 [[chalcogen]] elements showing a W-shaped alternation or secondary periodicity going down the group|alt=A graph with a vertical electronegativity axis and a horizontal atomic number axis. The five elements plotted are {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}, {{abbr|Te|tellurium}} and {{abbr|Po|polonium}}. The electronegativity of {{abbr|Se|selenium}} looks too high, and causes a bump in what otherwise be a smooth curve.]]
An alternation in certain periodic trends, sometimes referred to as [[Periodic table#Atomic radius|secondary periodicity]], becomes evident when descending groups 13 to 15, and to a lesser extent, groups 16 and 17.<ref>[[#Kneen|Kneen, Rogers & Simpson 1972, pp. 226, 360]]; [[#Siekierski|Siekierski & Burgess 2002, pp. 52, 101, 111, 124, 194]]</ref>{{efn|The net result is an even-odd difference between periods (except in the [[s-block]]): elements in even periods have smaller atomic radii and prefer to lose fewer electrons, while elements in odd periods (except the first) differ in the opposite direction. Many properties in the p-block then show a zigzag rather than a smooth trend along the group. For example, phosphorus and antimony in odd periods of group 15 readily reach the +5 oxidation state, whereas nitrogen, arsenic, and bismuth in even periods prefer to stay at +3.<ref>[[#Scerri2020|Scerri 2020, pp. 407–420]]</ref>}} Immediately after the first row of [[Block (periodic table)#d-block|d-block]] metals, from scandium to zinc, the 3d electrons in the [[Block (periodic table)#p-block|p-block]] elements—specifically, gallium (a metal), germanium, arsenic, selenium, and bromine—prove less effective at [[shielding effect|shielding]] the increasing positive nuclear charge.

The Soviet chemist {{Interlanguage link|Shchukarev|2=ru|3=Щукарев, Сергей Александрович|preserve=1}} gives two more tangible examples:<ref>[[#Shchukarev|Shchukarev 1977, p. 229]]</ref>
:<span style="font-size:95%">"The toxicity of some arsenic compounds, and the absence of this property in analogous compounds of phosphorus [P] and antimony [Sb]; and the ability of [[selenic acid]] [{{chem2|H2SeO4}}] to bring metallic gold [Au] into solution, and the absence of this property in sulfuric [[sulfuric acid|[{{chem2|H2SO4}}]]] and [[telluric acid|[{{chem2|H2TeO4}}]]] acids."</span>

====Higher oxidation states====
:''Roman numerals such as III, V and VIII denote oxidation states''

Some nonmetallic elements exhibit [[oxidation state]]s that deviate from those predicted by the octet rule, which typically results in an oxidation state of –3 in group 15, –2 in group 16, –1 in group 17, and 0 in group 18. Examples include [[ammonia]] NH<sub>3</sub>, [[hydrogen sulfide]] H<sub>2</sub>S, [[hydrogen fluoride]] HF, and elemental xenon Xe. Meanwhile, the maximum possible oxidation state increases from +5 in [[pnictogen|group 15]], to +8 in [[noble gas|group 18]]. The +5 oxidation state is observable from period 2 onward, in compounds such as [[nitric acid]] HN(V)O<sub>3</sub> and [[phosphorus pentafluoride]] PCl<sub>5</sub>.{{efn|Oxidation states do not reflect the actual net charge of atoms in molecules or ions, they represents the valence which refers more to how many bonds there are. For instance carbon typically has a valence of +4, but that only means that it forms three bonds. Electronegative elements such as fluorine are conventionally associated with negative valence, while electropositive ones have positive valence.}} [[Oxidation state#List of oxidation states of the elements|Higher oxidation states]] in later groups emerge from period 3 onwards, as seen in [[sulfur hexafluoride]] SF<sub>6</sub>, [[iodine heptafluoride]] IF<sub>7</sub>, and [[xenon tetroxide|xenon(VIII) tetroxide]] XeO<sub>4</sub>. For heavier nonmetals, their larger atomic radii and lower electronegativity values enable the formation of compounds with higher oxidation numbers, supporting higher bulk [[coordination number]]s.<ref name="Cox" />

====Multiple bond formation====
[[File:Pentazenium.png|thumb|right|alt=A chain of five N's in a wing shape|Molecular structure of [[pentazenium]], a homopolyatomic cation of nitrogen with the formula N<sub>5</sub><sup>+</sup> and structure N−N−N−N−N.<ref>[[#Vij|Vij et al. 2001]]</ref>]]Period 2 nonmetals, particularly carbon, nitrogen, and oxygen, show a propensity to form multiple bonds. The compounds formed by these elements often exhibit unique [[stoichiometries]] and structures, as seen in the various nitrogen oxides,<ref name="Cox">[[#Cox2004|Cox 2004, p. 146]]</ref> which are not commonly found in elements from later periods.

==== Property overlaps ====
While certain elements have traditionally been classified as nonmetals and others as metals, some overlapping of properties occurs. Writing early in the twentieth century, by which time the era of modern chemistry had been well-established<ref>[[#Dorsey|Dorsey 2023, pp. 12–13]]</ref> (although not as yet more precise [[quantum chemistry]]) Humphrey<ref>[[#Humphrey|Humphrey 1908]]</ref> observed that:
:<span style="font-size:95%">... these two groups, however, are not marked off perfectly sharply from each other; some nonmetals resemble metals in certain of their properties, and some metals approximate in some ways to the non-metals.</span>

[[Image:brown-boron.jpg|thumb|right|alt=An open glass jar with a brown powder in it|Boron (here in its less stable amorphous form) shares some similarities with metals{{efn|Greenwood<ref>[[#Greenwood2001|Greenwood 2001, p.&nbsp;2057]]</ref> commented that: "The extent to which metallic elements mimic boron (in having fewer electrons than orbitals available for bonding) has been a fruitful cohering concept in the development of metalloborane chemistry&nbsp;... Indeed, metals have been referred to as "honorary boron atoms" or even as "flexiboron atoms". The converse of this relationship is clearly also valid."}}]]
Examples of metal-like properties occurring in nonmetallic elements include:
* Silicon has an electronegativity (1.9) comparable with metals such as cobalt (1.88), copper (1.9), nickel (1.91) and silver (1.93);<ref name="AylwardEN"/>
* The electrical conductivity of graphite exceeds that of some metals;{{efn|For example, the conductivity of graphite is 3 × 10<sup>4</sup> S•cm<sup>−1.</sup><ref name=Bog/> whereas that of [[manganese]] is 6.9 × 10<sup>3</sup> S•cm<sup>−1</sup>.<ref>[[#Desai|Desai, James & Ho 1984, p.&nbsp;1160]]</ref>}}
* Selenium can be drawn into a wire;<ref name="ReferenceF"/>
* Radon is the most metallic of the noble gases and begins to show some [[cation]]ic behavior, which is unusual for a nonmetal;<ref>[[#Stein1983|Stein 1983, p. 165]]</ref> and
* In extreme conditions, just over half of nonmetallic elements can form homopolyatomic cations.{{efn|A homopolyatomic cation consists of two or more atoms of the same element bonded together and carrying a positive charge, for example, N<sub>5</sub><sup>+</sup>, O<sub>2</sub><sup>+</sup> and Cl<sub>4</sub><sup>+</sup>. This is unusual behavior for nonmetals since cation formation is normally associated with metals, and nonmetals are normally associated with anion formation. Homopolyatomic cations are further known for carbon, phosphorus, antimony, sulfur, selenium, tellurium, bromine, iodine and xenon.<ref>[[#Engesser|Engesser & Krossing 2013, p. 947]]</ref>}}

Examples of nonmetal-like properties occurring in metals are:
*[[Tungsten]] displays some nonmetallic properties, sometimes being brittle, having a high electronegativity, and forming only anions in aqueous solution,<ref>[[#S&P|Schweitzer & Pesterfield 2010, p. 305]]</ref> and predominately acidic oxides.<ref name="Porterfield"/><ref>[[#Rieck|Rieck 1967, p. 97]]: Tungsten trioxide dissolves in [[hydrofluoric acid]] to give an [[oxyfluoride]] [[Coordination complex|complex]].</ref>
*[[Gold]], the "king of metals" has the highest [[electrode potential]] among metals, suggesting a preference for gaining rather than losing electrons. Gold's ionization energy is one of the highest among metals, and its electron affinity and electronegativity are high, with the latter exceeding that of some nonmetals. It forms the Au<sup>–</sup> auride anion and exhibits a tendency to bond to itself, behaviors which are unexpected for metals. In aurides (MAu, where M = Li–Cs), gold's behavior is similar to that of a halogen.<ref>[[#Wiberg|Wiberg 2001, p. 1279]]</ref> The reason for this is that gold has a large enough nuclear potential that the electrons have to be considered with [[Relativistic quantum mechanics|relativistic]] effects included, which changes some of the properties.<ref>{{Cite journal |last=Pyper |first=N. C. |date=2020-09-18 |title=Relativity and the periodic table |url=https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0305 |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |language=en |volume=378 |issue=2180 |article-number=20190305 |doi=10.1098/rsta.2019.0305 |pmid=32811360 |bibcode=2020RSPTA.37890305P |issn=1364-503X|url-access=subscription }}</ref>

A relatively recent development involves certain compounds of heavier p-block elements, such as silicon, phosphorus, germanium, arsenic and antimony, exhibiting behaviors typically associated with [[coordination compound|transition metal complexes]]. This is linked to a small energy gap between their [[HOMO and LUMO|filled and empty]] [[molecular orbitals]], which are the regions in a molecule where electrons reside and where they can be available for chemical reactions. In such compounds, this allows for unusual reactivity with small molecules like hydrogen (H<sub>2</sub>), [[ammonia]] (NH<sub>3</sub>), and [[ethylene]] (C<sub>2</sub>H<sub>4</sub>), a characteristic previously observed primarily in transition metal compounds. These reactions may open new avenues in [[catalyst|catalytic]] applications.<ref>[[#Power|Power 2010]]; [[#Crow|Crow 2013]]; [[#Weetman|Weetman & Inoue 2018]]</ref>

==Types {{anchor|Classes}}==
[[List of alternative nonmetal classes|Nonmetal classification schemes]] vary widely, with some accommodating as few as two subtypes and others up to seven. For example, the periodic table in the [[Encyclopaedia Britannica]] recognizes noble gases, halogens, and other nonmetals, and splits the elements commonly recognized as metalloids between "other metals" and "other nonmetals".<ref>[[#EB2021|Encyclopaedia Britannica 2021]]</ref> On the other hand, seven of twelve color categories on the Royal Society of Chemistry periodic table include nonmetals.<ref>[[#RSC2|Royal Society of Chemistry 2021]]</ref>{{efn| Of the twelve categories in the Royal Society periodic table, five only show up with the metal filter, three only with the nonmetal filter, and four with both filters. Interestingly, the six elements marked as metalloids (boron, silicon, germanium, arsenic, antimony, and tellurium) show under both filters.  Six other elements (113–118: nihonium, flerovium, moscovium, livermorium, tennessine, and oganesson), whose status is unknown, also show up under both filters but are not included in any of the twelve color categories.}}

{| class="wikitable floatright" style="font-size:120%;text-align:center; line-height: 95%;border-color:black;"
|-style="font-size:70% ; line-height: 95%;"
| style="border:none"|
| colspan=1 style="border:none;" |
| colspan=4 style="border:none;" |  '''Group''' (1, 13−18)
| colspan=2 style="border:none;text-align:right" |  '''Period'''
|-style="font-size:70% ; line-height: 95%; vertical-align:top;"
| style="border:none"|
| scope="col" style="border:none; width: 22px" | 13
| scope="col" style="border:none; width: 22px" | 14
| scope="col" style="border:none; width: 22px" | 15
| scope="col" style="border:none; width: 22px" | 16
| scope="col" style="border:none; width: 22px" | <u>1</u>/17
| scope="col" style="border:none; width: 22px" | 18
| scope="col" style="border:none; width: 22px" | {{nowrap|(1−6)}}
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=4 style="border:none" |
| style="background-color:#FFFFFF;border-bottom:2px solid black;border-right:2px solid black;" | [[hydrogen|H]]
| style="background-color:#9BCDFD;padding-bottom:3px;" | [[helium|He]]
| style="border:none; font-size:70%;" | '''1'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="background-color:#FC9A9B;" | [[boron|B]]
| style="background-color:#FFFFFF;" | [[carbon|C]]
| style="background-color:#FFFFFF;" | [[neon|N]]
| style="background-color:#FFFFFF;" | [[oxygen|O]]
| style="background-color:#FFFD9F;" | [[fluorine|F]]
| style="background-color:#9BCDFD;" | [[neon|Ne]]
| style="border:none; font-size:70%" | '''2'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="border:none;" | 
| style="background-color:#FC9A9B;" | [[silicon|Si]]
| style="background-color:#FFFFFF;" | [[phosphorus|P]]
| style="background-color:#FFFFFF;" | [[sulfur|S]]
| style="background-color:#FFFD9F;" | [[chlorine|Cl]]
| style="background-color:#9BCDFD;" | [[argon|Ar]]
| style="border:none; font-size:70%" | '''3'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="border:none;" |
| style="background-color:#FC9A9B;" | [[germanium|Ge]]
| style="background-color:#FC9A9B;" | [[arsenic|As]]
| style="background-color:#FFFFFF;" | [[selenium|Se]]
| style="background-color:#FFFD9F;" | [[bromine|Br]]
| style="background-color:#9BCDFD;" | [[krypton|Kr]]
| style="border:none; font-size:70%" | '''4'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=2 style="border:none;" |
| style="background-color:#FC9A9B;" | [[antimony|Sb]]
| style="background-color:#FC9A9B;" | [[tellurium|Te]]
| style="background-color:#FFFD9F;" | [[iodine|I]]
| style="background-color:#9BCDFD;" | [[xenon|Xe]]
| style="border:none; font-size:70%" | '''5'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=5 style="border:none;" |
| style="background-color:#9BCDFD;" | [[radon|Rn]]
| style="border:none; font-size:70%" | '''6'''
|-
|-
| colspan=8 style="border:none;" |
<!--
| colspan=8 |
{| 
| {{nbsp|15}}
| style="border:none;font-size:70%;text-align:left;" |
{{legend|#9BCDFD|Noble gas}}
{{legend|#FFFD9F|Halogen nonmetals}}
{{legend|#FFFFFF|Other nonmetals}}
{{legend|#FC9A9B|Metalloida}}
|}-->
|}
Starting on the right side of the periodic table, three types of nonmetals can be recognized:

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#9BCDFD|size=110%}} the inert noble gases—helium, neon, argon, krypton, xenon, radon;<ref name="Matson"/></div>

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#FFFD9F|size=110%}} the reactive halogen nonmetals—fluorine, chlorine, bromine, iodine;<ref>[[#Kernion|Kernion & Mascetta 2019, p. 191]]; [[#Cao|Cao et al. 2021, pp. 20–21]]; [[#Hussain|Hussain et al. 2023]]; also called "nonmetal halogens": [[#Chambers1982|Chambers & Holliday 1982, pp. 273–274]]; [[#Bohlmann|Bohlmann 1992, p. 213]]; [[#Jentzsch|Jentzsch & Matile 2015, p. 247]] or "stable halogens": [[#Vassilakis|Vassilakis, Kalemos & Mavridis 2014, p. 1]]; [[#Hanley|Hanley & Koga 2018, p. 24]]; [[#Kaiho|Kaiho 2017, ch.&nbsp;2, p. 1]]</ref> and</div>

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#FFFFFF|size=110%}} the mixed reactivity "unclassified nonmetals", a set with no widely used collective name—hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, selenium.{{efn|Varying configurations of these nonmetals have been referred to as, for example, basic nonmetals,<ref>[[#Williams|Williams 2007, pp. 1550–1561: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}]]</ref> bioelements,<ref>[[#Wächtershäuser|Wächtershäuser 2014, p. 5: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref> central nonmetals,<ref>[[#Hengeveld|Hengeveld & Fedonkin 2007, pp. 181–226: {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}]]</ref> CHNOPS,<ref>[[#Wakeman|Wakeman 1899, p. 562]]</ref> essential elements,<ref>[[#Fraps|Fraps 1913, p. 11: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|Si|silicon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Cl|chlorine}}]]</ref> "non-metals",<ref>[[#Parameswaran|Parameswaran at al. 2020, p. 210: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref>{{efn|The quote marks are not found in the source; they are used here to make it clear that the source employs the word ''non-metals'' as a formal term for the subset of chemical elements in question, rather than applying to nonmetals generally.}} orphan nonmetals,<ref>[[#Knight|Knight 2002, p. 148: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref> or redox nonmetals.<ref>[[#Fraústo|Fraústo da Silva & Williams 2001, p. 500: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref>}} The descriptive phrase ''unclassified nonmetals'' is used here for convenience.</div>

The elements in a fourth set are sometimes recognized as nonmetals:

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#FC9A9B|size=110%}} the generally unreactive{{efn|"Crystalline boron is relatively inert."<ref>[[#Zhu2022|Zhu et al. 2022]]</ref> Silicon "is generally highly unreactive."<ref>[[#Graves|Graves 2022]]</ref> "Germanium is a relatively inert semimetal."<ref>[[#Rosenberg|Rosenberg 2013, p. 847]]</ref> "Pure arsenic is also relatively inert."<ref>[[#Obodovskiy|Obodovskiy 2015, p. 151]]</ref>{{efn|Arsenic is stable in dry air. Extended exposure in moist air results in the formation of a black surface coating. "Arsenic is not readily attacked by water, alkaline solutions or non-oxidizing acids".<ref>[[#Greenwood|Greenwood & Earnshaw 2002, p. 552]]</ref> It can occasionally be found in nature in an uncombined form.<ref>[[#Eagleson1994|Eagleson 1994, p. 91]]</ref> It has a positive standard reduction potential (As → As<sup>3+</sup> + 3e &#61; +0.30 V), corresponding to a classification of semi-noble metal.<ref>[[#Huang|Huang 2018, pp. 30, 32]]</ref>}} "Metallic antimony is&nbsp;… inert at room temperature."<ref>[[#Orisakwe|Orisakwe 2012, p. 000]]</ref> "Compared to {{abbr|S|sulfur}} and {{abbr|Se|selenium}}, {{abbr|Te|tellurium}} has relatively low chemical reactivity."<ref>[[#Yin|Yin et al. 2018, p. 2]]</ref>}}  metalloids,<ref name="Moeller">[[#Moeller1989|Moeller et al. 1989, p. 742]]</ref> sometimes considered a third category distinct from metals and nonmetals—boron, silicon, germanium, arsenic, antimony, tellurium.</div>
{{Quote box
|quote = While many of the early workers attempted to classify elements none of their classifications were satisfactory. They were divided into metals and nonmetals, but some were soon found to have properties of both. These were called metalloids. This only added to the confusion by making two indistinct divisions where one existed before.<ref>[[#Whiteford|Whiteford & Coffin 1939, p. 239]]</ref>
|salign = 
|source = Whiteford & Coffin 1939, ''Essentials of College Chemistry''
| bgcolor = Lightyellow
| width = 220px
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| align = right
}}
The boundaries between these types are not sharp.{{efn|Boundary fuzziness and overlaps often occur in classification schemes.<ref name="Jones"/>}} Carbon, phosphorus, selenium, and iodine border the metalloids and show some metallic character, [[#Hlike a metal|as does hydrogen]].

The greatest discrepancy between authors occurs in metalloid "frontier territory".<ref>[[#Russell|Russell & Lee 2005, p. 419]]</ref> Some consider metalloids distinct from both metals and nonmetals, while others classify them as nonmetals.<ref name="Goodrich etc">[[#Goodrich|Goodrich 1844, p. 264]]; [[#TheChemical1897|''The Chemical News'' 1897, p. 189]]; [[#Hampel|Hampel & Hawley 1976, pp. 174, 191]]; [[#Lewis|Lewis 1993, p. 835]]; [[#Hérold|Hérold 2006, pp. 149–50]]</ref> Some categorize certain metalloids as metals (e.g., arsenic and antimony due to their similarities to [[heavy metals]]).<ref>[[#Tyler|Tyler 1948, p. 105]]; [[#Reilly|Reilly 2002, pp. 5–6]]</ref>{{efn|Jones takes a philosophical or pragmatic view to these questions. He writes: "Though classification is an essential feature of all branches of science, there are always hard cases at the boundaries. The boundary of a class is rarely sharp{{nbsp}}... Scientists should not lose sleep over the hard cases. As long as a classification system is beneficial to economy of description, to structuring knowledge and to our understanding, and hard cases constitute a small minority, then keep it. If the system becomes less than useful, then scrap it and replace it with a system based on different shared characteristics."<ref name="Jones">[[#Jones|Jones 2010, pp. 169–71]]</ref>}} Metalloids resemble the elements universally considered "nonmetals" in having relatively low densities, high electronegativity, and similar chemical behavior.<ref name="Moeller"/>{{efn|For a related comparison of the [[properties of metals, metalloids, and nonmetals]], see [[#RDM|Rudakiya & Patel (2021), p. 36.]]}}

=== Noble gases ===
{{main|Noble gas}}
[[File:Argon ice 1.jpg|thumb|A small (about 2 cm long) piece of rapidly melting [[argon]] ice|alt=a glass tube, held upside down by some tongs, has a clear-looking ice-like plug in it which is slowly melting judging from the clear drops falling out of the open end of the tube]]
Six nonmetals are classified as noble gases: helium, neon, argon, krypton, xenon, and the radioactive radon. In conventional periodic tables they occupy the rightmost column. They are called ''noble'' gases due to their exceptionally low [[chemical reactivity]].<ref name="Matson">[[#Matson|Matson & Orbaek 2013, p. 203]]</ref>

These elements exhibit similar properties, being colorlessness, odorless, and nonflammable. Due to their closed outer electron shells, noble gases possess weak [[interatomic force]]s of attraction, leading to exceptionally low melting and boiling points.<ref>[[#Jolly|Jolly 1966, p. 20]]</ref>

Chemically, the noble gases exhibit relatively high ionization energies, negligible or negative electron affinities, and high to very high electronegativities. The number of compounds formed by noble gases is in the hundreds and continues to expand,<ref>[[#Maosheng|Maosheng 2020, p. 962]]</ref> with most of these compounds involving the combination of oxygen or fluorine with either krypton, xenon, or radon.<ref>[[#Mazej|Mazej 2020]]</ref>

=== Halogen nonmetals ===
{{Main|Halogen}}Chemically, the halogen nonmetals have high ionization energies, electron affinities, and electronegativity values, and are relatively strong [[oxidizing agent]]s.<ref name="oxidizing">[[#Rudolph|Rudolph 1973, p. 133]]: "Oxygen and the halogens in particular{{nbsp}}... are therefore strong oxidizing agents."</ref> All four elements tend to form primarily [[ionic compound]]s with metals,<ref name="Cotton">[[#Cotton|Cotton et al. 1999, p. 554]]</ref> in contrast to the remaining nonmetals (except for oxygen) which tend to form primarily [[covalent compound]]s with metals.{{efn|Metal oxides are usually somewhat ionic, depending upon the metal element electropositivity.<ref>[[#Woodward|Woodward et al. 1999, pp. 133–194]]</ref> On the other hand, oxides of metals with high oxidation states are often either polymeric or covalent.<ref>[[#Phillips1965|Phillips & Williams 1965, pp. 478–479]]</ref> A polymeric oxide has a linked structure composed of multiple repeating units.<ref>[[#Moeller1989|Moeller et al. 1989, p. 314]]</ref>}}

=== Unclassified nonmetals ===
{{anchor|Unclassified nonmetal|right}}

[[File:Selenium black (cropped).jpg|thumb|right|[[Selenium]] conducts electricity around 1,000 times better [[photoconductor|when light falls on it]], a property used in [[Photodetector|light-sensing applications]].<ref>[[#Emsley2011|Emsley 2011, p. 478]]</ref>|alt=A small glass jar filled with small dull grey concave buttons. The pieces of selenium look like tiny mushrooms without their stems.]]

{{Anchor|Hlike a metal}}Hydrogen behaves in some respects like a metallic element and in others like a nonmetal.<ref>[[#Seese|Seese & Daub 1985, p. 65]]</ref> Like a metallic element it can, for example, form a [[solvation|solvated cation]] in [[aqueous solution]];<ref>[[#MacKay|MacKay, MacKay & Henderson 2002, pp. 209, 211]]</ref> it can substitute for [[alkali metal]]s in compounds such as the chlorides ([[sodium chloride|NaCl]] cf. [[hydrochloric acid|HCl]]) and nitrates ([[potassium nitrate|KNO<sub>3</sub>]] cf. [[nitric acid|HNO<sub>3</sub>]]), and in certain alkali metal [[organometallic chemistry|complexes]]<ref>[[#Cousins|Cousins, Davidson & García-Vivó 2013, pp. 11809–11811]]</ref><ref name="Cao4">[[#Cao|Cao et al. 2021, p. 4]]</ref> as a nonmetal.<ref>[[#Liptrot|Liptrot 1983, p. 161]]; [[#MD|Malone & Dolter 2008, p. 255]]</ref> It attains this configuration by forming a covalent or ionic bond<ref name="Wiberg255–257">[[#Wiberg|Wiberg 2001, pp. 255–257]]</ref> or by bonding as an ion to a lone pair of electrons.<ref>[[#Scott1962|Scott & Kanda 1962, p. 153]]</ref>

Some or all of these nonmetals share several properties. Being generally less reactive than the halogens,<ref>[[#Taylor|Taylor 1960, p. 316]]</ref> most of them can occur naturally in the environment.<ref name="Emsley"/> Collectively, their physical and chemical characteristics can be described as "moderately non-metallic".<ref name="Cao20">[[Nonmetal#Cao|Cao et al. 2021, p. 20]]</ref> When combined with metals, the unclassified nonmetals can form [[interstitial compound|interstitial]] or [[refractory]] compounds.<ref>[[#Mess|Messler 2011, p. 10]]</ref> They also exhibit a tendency to [[catenation|bond to themselves]], particularly in solid compounds.<ref>[[#King1994|King 1994, p. 1344]]; [[#Powell|Powell & Tims 1974, pp. 189–191]]; [[#Cao|Cao et al. 2021, pp. 20–21]]</ref> Additionally, [[Diagonal relationship|diagonal periodic table relationships]] among these nonmetals mirror similar relationships among the metalloids.<ref>[[#Vernon2020|Vernon 2020, pp. 221–223]]; [[#RaynerW|Rayner-Canham 2020, p. 216]]</ref>

==Abundance, extraction, and uses==

===Abundance===
{| class="wikitable floatright" style="font-size: 95%; white-space:nowrap;"
|-
|+ Approximate composition <br/> {{nobold|''(top three components by weight; elements marked {{legend inline | #FFF2CC
| border    = 1px solid black
| textcolor = black
| size      = 90%
| text      = *nonmetal
}} {{legend inline | white
| border    = 1px solid black
| textcolor = black
| size      = 90%
| text      = metal
}}}}
|-
| '''Universe'''<ref>[[#Chandra|Chandra X-ray Center 2018]]</ref>
| style="background-color:#FFF2CC" |  75% *hydrogen
| style="background-color:#FFF2CC" |  23% *helium 
| style="background-color:#FFF2CC" |   1% *oxygen
<!--
| style="background-color:#FFF2CC" |  x% *other nonmetals 
| style="background-color:white" |  x% all metals
-->
|-
| '''Atmosphere'''<ref>[[#Chapin|Chapin, Matson & Vitousek 2011, p. 27]]</ref>
| style="background-color:#FFF2CC" |  78% *nitrogen 
| style="background-color:#FFF2CC" |  21% *oxygen 
| style="background-color:#FFF2CC" |  0.5% *argon
<!--
| style="background-color:#FFF2CC" |  x% *other nonmetals 
| style="background-color:white" |  x% all metals
-->
|-
| '''Hydrosphere'''<ref name=Fortescue>[[#Fortescue|Fortescue 1980, p. 56]]</ref>
| style="background-color:#FFF2CC" |  86% *oxygen 
| style="background-color:#FFF2CC" |  11% *hydrogen 
| style="background-color:#FFF2CC" |   2% *chlorine
<!--
| style="background-color:#FFF2CC" |  x% *other nonmetals 
| style="background-color:white" |  x% all metals
-->
|-
| '''Biomass'''<ref>[[#Georgievskii|Georgievskii 1982, p. 58]]</ref>
| style="background-color:#FFF2CC" |  63% *oxygen 
| style="background-color:#FFF2CC" |  20% *carbon 
| style="background-color:#FFF2CC" |  10% *hydrogen
<!--
| style="background-color:#FFF2CC" |  x% *other nonmetals 
| style="background-color:white" |  x% all metals
-->
|-
| '''Crust'''<ref name=Fortescue/> 
| style="background-color:#FFF2CC" |  46% *oxygen 
| style="background-color:#FFF2CC" |  27% *silicon 
| style="background-color:white" |  8% aluminium
<!--
| style="background-color:#FFF2CC" |  x% *other nonmetals 
| style="background-color:white" |  x% other metals
-->
|-
| '''Earth'''<ref name=":2">[[#Morgan|Morgan & Anders 1980, p. 6975]]</ref>
| style="background-color:white" |  32% iron
| style="background-color:#FFF2CC" |  30% *oxygen
| style="background-color:white" |  14% magnesium 
<!--
| style="background-color:#FFF2CC" |  x% *other nonmetals 
| style="background-color:white" |  x% other metals
-->
|}
The [[abundance of chemical elements|abundance of elements]] in the universe results from nuclear physics processes like [[nucleosynthesis]] and [[radioactive decay]].

The volatile noble gas nonmetal elements are less abundant in the atmosphere than expected based upon their overall abundance due to cosmic [[nucleosynthesis]]. Mechanisms to explain this difference is an important aspect of [[planetary science]].<ref>{{Cite journal |last1=Pepin |first1=R. O. |last2=Porcelli |first2=D. |date=2002-01-01 |title=Origin of Noble Gases in the Terrestrial Planets |journal=Reviews in Mineralogy and Geochemistry |volume=47 |issue=1 |pages=191–246 |doi=10.2138/rmg.2002.47.7 |bibcode=2002RvMG...47..191P |issn=1529-6466}}</ref> The element {{abbr|Xe|xenon}} is unexpectedly depleted, and a possible explanation comes from theoretical models of the high pressures in the Earth's core suggesting that there may be around 10<sup>13</sup> tons of xenon in the form of stable XeFe<sub>3</sub> and XeNi<sub>3</sub> [[intermetallic compound]]s.<ref>[[#Zhu2014|Zhu et al. 2014, pp. 644–648]]</ref>

Five nonmetals—hydrogen, carbon, nitrogen, oxygen, and silicon—form the bulk of the directly observable structure of the Earth: about 73% of the [[Earth's crust|crust]], 93% of the [[biomass (ecology)|biomass]], 96% of the [[hydrosphere]], and over 99% of the [[Earth's atmosphere|atmosphere]], as shown in the accompanying table. Silicon and oxygen form stable tetrahedral structures, known as [[silicate mineral|silicates]]. Here, "the powerful bond that unites the oxygen and silicon ions is the cement that holds the Earth's crust together."<ref>[[#Klein|Klein & Dutrow 2007, p. 435]]</ref> However, they make up less than 50% of the total weight of the earth.<ref name=":2" />

In the biomass, the relative abundance of the first four nonmetals (and phosphorus, sulfur, and selenium marginally) is attributed to a combination of relatively small atomic size, and sufficient spare electrons. These two properties enable them to bind to one another and "some other elements, to produce a molecular soup sufficient to build a self-replicating system."<ref>[[Cockell|Cockell 2019, p. 212, 208–211]]</ref>

===Extraction===
Nine of the 23 nonmetallic elements are gases, or form compounds that are gases, and are extracted from [[natural gas]] or [[liquid air]], including hydrogen, nitrogen, oxygen, sulfur, and most of the noble gases. For example, nitrogen and oxygen are extracted from liquid air through [[fractional distillation]]<ref>[[#Emsley2011|Emsley 2011, pp. 363, 379]]</ref> and  sulfur from the hydrogen sulfide in natural gas by reacting it with oxygen to yield water and sulfur.<ref>[[#Emsley2011|Emsley 2011, p. 516]]</ref> Three nonmetals are extracted from seawater; the rest of the nonmetals – and almost all metals – from mining solid ores.{{citation needed |date=April 2025}}

{| class="wikitable floatright" style="font-size:120%;text-align:center; line-height: 95%;border-color:black;"
|-style="font-size:70% ; line-height: 95%;"
| style="border:none"|
| colspan=1 style="border:none;" |
| colspan=4 style="border:none;" |  '''Group''' (1, 13−18)
| colspan=2 style="border:none;text-align:right" |  '''Period'''
|-style="font-size:70% ; line-height: 95%; vertical-align:top;"
| style="border:none"|
| scope="col" style="border:none; width: 22px" | 13
| scope="col" style="border:none; width: 22px" | 14
| scope="col" style="border:none; width: 22px" | 15
| scope="col" style="border:none; width: 22px" | 16
| scope="col" style="border:none; width: 22px" | <u>1</u>/17
| scope="col" style="border:none; width: 22px" | 18
| scope="col" style="border:none; width: 22px" | {{nowrap|(1−6)}}
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=4 style="border:none" |
| style="background-color:yellow; ng;border-bottom:2px solid black;border-right:2px solid black;" |  H
| style="background-color:yellow; ng;padding-bottom:3px;" |  He
| style="border:none; font-size:70%;" | '''1'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="background-color:#FF9999;mo;" |B
| style="background-color:#FF9999;mo;" |C
| style="background-color:lightskyblue; la;" |N
| style="background-color:lightskyblue; la;" |O
| style="background-color:#FF9999;mo;" |F
| style="background-color:lightskyblue; la;" |Ne
| style="border:none; font-size:70%" | '''2'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="border:none;" | 
| style="background-color:#FF9999;mo;" |Si
| style="background-color:#FF9999;mo;" |P
| style="background-color:yellow; ng;" |S
| style="background-color:lightseagreen; sb;" |Cl
| style="background-color:lightskyblue; la;" |Ar
| style="border:none; font-size:70%" | '''3'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="border:none;" |
| style="background-color:#FF9999;mb;" |Ge
| style="background-color:#FF9999;mb;" |As
| style="background-color:#FF9999;mb;" |Se
| style="background-color:lightseagreen; sb;" |Br
| style="background-color:lightskyblue; la;" |Kr
| style="border:none; font-size:70%" | '''4'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=2 style="border:none;" |
| style="background-color:#FF9999;mo;" |Sb
| style="background-color:#FF9999;mb;" |Te
| style="background:linear-gradient(45deg, #FF9999 0 50%, lightseagreen 50% 100%); sb;" mo |I
| style="background-color:lightskyblue; la;" |Xe
| style="border:none; font-size:70%" | '''5'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=5 style="border:none;" |
| style="background-color:#FF9999;mb;" |Rn
| style="border:none; font-size:70%" | '''6'''
|-
| colspan=8 style="border:none;" |
|}
{{nowrap|Nonmetallic elements}} are extracted from these sources:<ref name="Emsley">[[#Emsley2011|Emsley 2011, ''passim'']]</ref>

;{{legend inline|yellow |size=110%|text=3}}from natural gas components: hydrogen ([[methane]]), helium, and sulfur ([[hydrogen sulfide]])

;{{legend inline|lightskyblue| size=110%|text=6}}from [[liquefied air]]: nitrogen, oxygen, neon, argon, krypton, and xenon

;{{legend inline|lightseagreen |size=110%|text=3}}from seawater [[brine]]: chlorine, bromine, and iodine

;{{legend inline|#FF9999| size=110%|text=12}}from solid ores: boron ([[borate]]s), carbon (natural graphite), silicon ([[silica]]), phosphorus ([[phosphate]]s), iodine ([[sodium iodate]]), radon ([[uranium ore]] decay product), fluorine ([[fluorite]]);  and germanium, arsenic, selenium, antimony, and tellurium (from their [[sulfide]]s).

===Uses===
[[File:Argon.jpg|alt=seven large red cylinders, with green tops, side by side in a rack|thumb|right|270x270px|Cylinders containing argon gas for use in extinguishing fire without damaging [[computer server]] equipment]]
Nonmetallic elements are present in combination with other elements in almost everything around us, from water to plastics and within metallic alloys. There are some specific uses of the elements themselves, although these are less common; extensive details can be found in the specific pages of the relevant elements. A few examples are:

# Hydrogen can be used in [[fuel cell]]s, and is being explored for a possible future low-carbon [[hydrogen economy]].<ref>{{Cite journal |last1=Cheng |first1=Xuan |last2=Shi |first2=Zheng |last3=Glass |first3=Nancy |last4=Zhang |first4=Lu |last5=Zhang |first5=Jiujun |last6=Song |first6=Datong |last7=Liu |first7=Zhong-Sheng |last8=Wang |first8=Haijiang |last9=Shen |first9=Jun |date=2007-03-20 |title=A review of PEM hydrogen fuel cell contamination: Impacts, mechanisms, and mitigation |url=https://linkinghub.elsevier.com/retrieve/pii/S0378775306025304 |journal=Journal of Power Sources |series=IBA – HBC 2006 |volume=165 |issue=2 |pages=739–756 |doi=10.1016/j.jpowsour.2006.12.012 |bibcode=2007JPS...165..739C |issn=0378-7753|url-access=subscription }}</ref>
# Carbon has many uses, ranging from decorative applications of [[Diamond (gemstone)|diamond jewelry]]<ref>{{Cite journal |last=Purbrick |first=L. |date=2011-02-22 |title=Brilliant Effects: A Cultural History of Gem Stones and Jewellery |journal=Journal of Design History |volume=24 |issue=1 |pages=88–90 |doi=10.1093/jdh/epq052 |issn=0952-4649}}</ref> to diamond in [[Diamond cutting|cutting blades]]<ref>{{Cite book |last=Harlow |first=George E. |title=The nature of diamonds |date=1997 |publisher=Cambridge University Press in association with the American Museum of Natural History |others=American museum of natural history |isbn=978-0-521-62083-3 |location=Cambridge}}</ref> and graphite as a [[solid lubricant]].<ref name=":1" />
# [[Liquid nitrogen]] is extensively used as a coolant.<ref>{{Cite web |last1=Beteta |first1=Oscar |last2=Ivanova |first2=Svetlana |date=September 2015 |title=Cool down with liquid nitrogen |url=https://www.aiche.org/sites/default/files/cep/20150930.pdf |website=American Institute of Chemical Engineers}}</ref>
# Oxygen is a critical component of the air we breath. (While nitrogen is also present, it is less used from the air, mainly by certain bacteria.<ref>{{Cite journal |last1=Franche |first1=Claudine |last2=Lindström |first2=Kristina |last3=Elmerich |first3=Claudine |date=2009 |title=Nitrogen-fixing bacteria associated with leguminous and non-leguminous plants |url=http://link.springer.com/10.1007/s11104-008-9833-8 |journal=Plant and Soil |language=en |volume=321 |issue=1–2 |pages=35–59 |doi=10.1007/s11104-008-9833-8 |bibcode=2009PlSoi.321...35F |issn=0032-079X|url-access=subscription }}</ref>) Oxygen gas and liquid is also heavily used for combustion in [[Oxy-fuel welding and cutting|welding and cutting torches]] and as a component of [[rocket fuels]].<ref>{{Cite web |title=Basics of Space Flight: Rocket Propellants |url=http://www.braeunig.us/space/propel.htm |access-date=2025-04-24 |website=www.braeunig.us}}</ref>
# Silicon is the most widely used semiconductor. While ultra-pure silicon is an insulator, by selectively adding [[Doping (semiconductor)|electronic dopants]] it can be used as a [[semiconductor]] where the [[chemical potential]] of the electrons can be manipulated, this being exploited in a wide range of [[electronic devices]].<ref name=":0" />
# The noble gases have a range of applications, including [[liquid helium]] for [[cryogenic cooling]],<ref>{{Cite web |title=4 Ways Cryogenic Applications of Helium Can Be Used |url=https://www.cryogenicsociety.org/index.php?option=com_dailyplanetblog&view=entry&category=industry-news&id=189:4-ways-cryogenic-applications-of-helium-can-be-used |access-date=2025-04-24 |website=www.cryogenicsociety.org}}</ref> and argon to in [[gaseous fire suppression]] to -damp fires around sensitive electrical equipment where water cannot be used.<ref>{{Cite web |last=Peters |first=M. J. |title=Which Gases Are Used in Fire Suppression Systems? |url=https://www.firetrace.com/fire-protection-blog/gases-used-in-fire-suppression-systems |access-date=2025-04-24 |website=www.firetrace.com |language=en}}</ref>
# Radon is a potentially hazardous indoor pollutant.<ref>[[#Maroni|Maroni 1995, pp.&nbsp;108–123]]</ref>

== Taxonomical history ==
===Background===
Medieval [[alchemist|chemical philosophers]] focused on metals, rarely investigating nonmetallic minerals.<ref>[[#Stillman|Stillman 1924, p. 213]]</ref>

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| align = right
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| image2= Portrait of A.L. Lavoisier. Wellcome M0011209.jpg
| alt2= A distinguished gentleman, seated and looking towards the view; a copy of his book "Traité élémentaire de chimie" is at his hand upon what looks to be a reading plinth
 | caption2= 
| image1=Lavoisiers elements.gif
| alt1=
| caption1=
| footer = French nobleman and chemist [[Antoine Lavoisier]] (1743–1794), with a page of the English translation of his 1789 ''[[Traité élémentaire de chimie]]'',<ref>[[#Lavoisier|Lavoisier 1790, p. 175]]</ref> listing the elemental gases oxygen, hydrogen and nitrogen (and erroneously including [[light]] and [[caloric theory|caloric]]); the nonmetallic substances sulfur, phosphorus, and carbon; and the [[chloride]], [[fluoride]] and [[borate]] ions
}}

===Organization of elements by types===
{{see also | Discovery of chemical elements}}
In the late 1700s, French chemist [[Antoine Lavoisier]] published the first modern list of chemical elements in his revolutionary<ref>[[#Strathern2000|Strathern 2000, p. 239]]</ref> 1789 ''[[Traité élémentaire de chimie]]''. The 33 elements known to Lavoisier were categorized into four distinct groups, including gases, metallic substances, nonmetallic substances that form acids when oxidized,<ref name=Moore1918>{{Cite book |last1=Moore  |first1=F. J. |url=https://archive.org/details/historyofchemist030951mbp/page/n125/mode/2up?q=lavoisier |title=A History Of Chemistry |last2=Hall |first2=William T. |publisher=McGraw-Hill |year=1918 |page=99 |access-date=2024-08-01}} Lavoisier's Table is reproduced on page 99.</ref> and [[Earth (historical chemistry)|earths]] (heat-resistant oxides).<ref>[[#Criswell|Criswell 2007, p. 1140]]</ref> Lavoisier's work gained widespread recognition and was republished in twenty-three editions across six languages within its first seventeen years, significantly advancing the understanding of chemistry in Europe and America.<ref>[[#Salzberg|Salzberg 1991, p. 204]]</ref>  Lavoisier's chemistry was "dualistic",: "salts" were combinations of "acid" and "base"; acids where combinations of oxygen and metals while bases where combinations of oxygen and nonmetals. This view prevailed despite increasing evidence that chemicals like [[chlorine]] and [[ammonia]] contained no oxygen, in large part due the vigious if sometimes misguided defense by the Swedish chemist [[Jöns Jacob Berzelius|Berzelius]].<ref name=Moore1918/>{{rp|165}}

In 1802 the term "metalloids" was introduced for elements with the physical properties of metals but the chemical properties of non-metals.<ref name="Friend1953">Friend JN 1953, ''Man and the Chemical Elements,'' 1st ed., Charles Scribner's Sons, New York</ref> In 1811 Berzelius used the term "metalloids"<ref>[[#Berzelius|Berzelius 1811, p. 258]]</ref> to describe all nonmetallic elements, noting their ability to form [[oxyanion|negatively charged ions with oxygen]] in [[aqueous solution]]s.<ref>[[#Partington1964|Partington 1964, p.&nbsp;168]]</ref><ref name="B1832">[[#Bache|Bache 1832, p.&nbsp;250]]</ref> Drawing on this, in 1864 the "Manual of Metalloids" divided all elements into either metals or metalloids, with the latter group including elements now called nonmetals.<ref>Apjohn, J. (1864). Manual of the Metalloids. United Kingdom: Longman.</ref>{{rp|31}}  Reviews of the book indicated that the term "metalloids" was still endorsed by leading authorities,<ref name="Thechemical1864">[[#Thechemical1864|''The Chemical News and Journal of Physical Science'' 1864]]</ref> but there were reservations about its appropriateness. While Berzelius' terminology gained significant acceptance,<ref name="goldsmith">[[#Goldsmith|Goldsmith 1982, p.&nbsp;526]]</ref> it later faced criticism from some who found it counterintuitive,<ref name="B1832"/> misapplied,<ref name=r4>[[#Roscoe|Roscoe & Schormlemmer 1894, p.&nbsp;4]]</ref> or even invalid.<ref>[[#Glinka1960|Glinka 1960, p.&nbsp;76]]</ref>  The idea of designating elements like [[arsenic]] as metalloids had been considered.<ref name="Thechemical1864"/> The use of the term "metalloids" persisted in France as textbooks of chemistry appeared in the 1800s. During this period, "metals" as a chemical category were characterized by a single property, their affinity for oxygen, while "metalloids" were organized by comparison of many characteristic analogous to the approach of [[naturalists]].<ref>[[#Bertomeu|Bertomeu-Sánchez et al. 2002, pp. 235]]</ref>
{{clear}}

===Development of types===
[[File:Lyon 1er - Place Gabriel Rambaud - Monument aux Grands Hommes de la Martinière - Gaspard Alphonse Dupasquier (medaillon).jpg|thumb|Bust of Dupasquier (1793–1848) in the {{ill|Monument aux Grands Hommes de la Martinière|fr}} in [[Lyon]], [[France]].|alt=A side profile set in stone of a distinguished French gentleman]]

In 1844, {{ill|Alphonse Dupasquier|fr|Gaspard Alphonse Dupasquier}}, a French doctor, pharmacist, and chemist,<ref>[[#Bertomeu|Bertomeu-Sánchez et al. 2002, pp. 248–249]]</ref> established a basic taxonomy of nonmetals to aid in their study. He wrote:<ref>[[#Dupasquier|Dupasquier 1844, pp. 66–67]]</ref>

:<span style="font-size:95%">They will be divided into four groups or sections, as in the following:</span>
::<span style="font-size:95%">Organogens—oxygen, nitrogen, hydrogen, carbon</span>
::<span style="font-size:95%">Sulphuroids—sulfur, selenium, phosphorus</span>
::<span style="font-size:95%">Chloroides—fluorine, chlorine, bromine, iodine</span>
::<span style="font-size:95%">Boroids—boron, silicon.</span>

Dupasquier's quartet parallels the modern nonmetal types. The organogens and sulphuroids are akin to the unclassified nonmetals. The chloroides were later called halogens.<ref>[[#Bache|Bache 1832, pp. 248–276]]</ref> The boroids eventually evolved into the metalloids, with this classification beginning from as early as 1864.<ref name="Thechemical1864"/> The then unknown noble gases were recognized as a distinct nonmetal group after being discovered in the late 1800s.<ref>[[#Renouf|Renouf 1901, pp. 268]]</ref> This taxonomy was noted as a "natural classification" of the substance considering all aspects rather than an single characteristic like oxygen affinity.<ref>[[#Bertomeu|Bertomeu-Sánchez et al. 2002, p. 236]]</ref> It was a significant departure from other contemporary classifications, since it grouped together oxygen, nitrogen, hydrogen, and carbon.<ref>[[#Hoefer|Hoefer 1845, p. 85]]</ref>

In 1828 and 1859, the French chemist [[Jean-Baptiste Dumas|Dumas]] classified nonmetals as (1) hydrogen; (2) fluorine to iodine; (3) oxygen to sulfur; (4) nitrogen to arsenic; and (5) carbon, boron and silicon,<ref>[[#Dumas1828|Dumas 1828]]; [[#Dumas1859|Dumas 1859]]</ref> thereby anticipating the vertical groupings of Mendeleev's 1871 periodic table. Dumas' five classes fall into modern groups [[Properties of nonmetals (and metalloids) by group#Group 1|1]], [[Properties of nonmetals (and metalloids) by group#Group 17|17]], [[Properties of nonmetals (and metalloids) by group#Group 16|16]], [[Properties of nonmetals (and metalloids) by group#Group 15|15]], and [[Properties of nonmetals (and metalloids) by group#Group 14|14]] to
[[Properties of nonmetals (and metalloids) by group#Group 13|13]] respectively.

=== Nonmetals as terminology ===
By as early as 1866, some authors began preferring the term "nonmetal" over "metalloid" to describe nonmetallic elements.<ref>[[#OED1989|Oxford English Dictionary 1989]]</ref> In 1875, Kemshead<ref>[[#kemshead|Kemshead 1875, p.&nbsp;13]]</ref> observed that elements were categorized into two groups: non-metals (or metalloids) and metals. He noted that the term "non-metal", despite its compound nature, was more precise and had become universally accepted as the nomenclature of choice.

=== Structure, quantum mechanics and band structure ===
The early terminologies were empirical categorizations based upon observables. As the 20th century started there were significant changes in understanding. The first was due to methods, mainly [[x-ray crystallography]], for determining how atoms are arranged in the various materials. As early as 1784 [[René Just Haüy]] discovered that every face of a crystal could be described by simple stacking patterns of blocks of the same shape and size ([[Law of rational indices|law of decrements]]).<ref>{{Cite book |last=Authier |first=André |title=Early days of X-ray crystallography |date=2013 |publisher=Oxford university press |isbn=978-0-19-965984-5 |location=Oxford}}</ref>  Haüy's study led to the idea that crystals are a regular three-dimensional array (a [[Bravais lattice]]) of atoms and [[molecule]]s, with a single [[unit cell]] repeated indefinitely, along with other developments in the [[Physical crystallography before X-rays|early days of physical crystallography]]. After [[Max von Laue]] demonstrated in 1912 that x-rays diffract,<ref>{{cite journal |vauthors=von Laue M |date=1914 |title=Concerning the detection of x-ray interferences |url=http://nobelprize.org/nobel_prizes/physics/laureates/1914/laue-lecture.pdf |url-status=live |journal=Nobel Lectures, Physics |volume=1901–1921 |archive-url=https://web.archive.org/web/20101207113911/http://nobelprize.org/nobel_prizes/physics/laureates/1914/laue-lecture.pdf |archive-date=2010-12-07 |access-date=2009-02-18}}</ref> fairly quickly [[William Lawrence Bragg]] and his father [[William Henry Bragg]] were able to solve previously unknown structures.<ref>{{cite journal |vauthors=Bragg WL |date=1913 |title=The Structure of Some Crystals as Indicated by their Diffraction of X-rays |journal=Proc. R. Soc. Lond. |volume=A89 |issue=610 |pages=248–277 |bibcode=1913RSPSA..89..248B |doi=10.1098/rspa.1913.0083 |jstor=93488 |doi-access=free}}</ref><ref>{{cite journal |vauthors=Bragg WL, James RW, Bosanquet CH |date=1921 |title=The Intensity of Reflexion of X-rays by Rock-Salt |url=https://zenodo.org/record/1430965 |url-status=live |journal=Phil. Mag. |volume=41 |issue=243 |page=309 |doi=10.1080/14786442108636225 |archive-url=https://web.archive.org/web/20200329132638/https://zenodo.org/record/1430965 |archive-date=2020-03-29 |access-date=2019-09-10}}</ref><ref>{{cite journal |vauthors=Bragg WL, James RW, Bosanquet CH |date=1921 |title=The Intensity of Reflexion of X-rays by Rock-Salt. Part II |url=https://zenodo.org/record/1430951 |url-status=live |journal=Phil. Mag. |volume=42 |issue=247 |page=1 |doi=10.1080/14786442108633730 |archive-url=https://web.archive.org/web/20200329132627/https://zenodo.org/record/1430951 |archive-date=2020-03-29 |access-date=2019-09-10}}</ref> Building on this, it became clear that most of the simple elemental metals had [[close packed]] structures. With this determined the concept of [[dislocation]]s originally developed by [[Vito Volterra]] in 1907<ref>[[Vito Volterra]] (1907) [https://eudml.org/doc/81250 "Sur l'équilibre des corps élastiques multiplement connexes"], ''Annales Scientifiques de l'École Normale Supérieure'', Vol. 24, pp. 401–517</ref> became accepted, for instance being used to explain the ductility of metals by [[G. I. Taylor]] in 1934.<ref>{{cite journal |author=G. I. Taylor |author-link=G. I. Taylor |year=1934 |title=The Mechanism of Plastic Deformation of Crystals. Part I. Theoretical |journal=Proceedings of the Royal Society of London. Series A |volume=145 |issue=855 |pages=362–87 |bibcode=1934RSPSA.145..362T |doi=10.1098/rspa.1934.0106 |jstor=2935509 |doi-access=free}}</ref>

The second was the advent of quantum mechanics. In 1924 [[Louis de Broglie]] in his PhD thesis ''Recherches sur la théorie des quanta''<ref name="Broglie">{{cite web |last1=de Broglie |first1=Louis Victor |title=On the Theory of Quanta |url=https://fondationlouisdebroglie.org/LDB-oeuvres/De_Broglie_Kracklauer.pdf |access-date=25 February 2023 |website=Foundation of Louis de Broglie |edition=English translation by A.F. Kracklauer, 2004.}}</ref> introduced his theory of [[electron]] waves. This rapidly became part of what was called by [[Erwin Schrödinger]] ''undulatory mechanics'',<ref name="Schroedinger">{{Cite journal |last=Schrödinger |first=E. |date=1926 |title=An Undulatory Theory of the Mechanics of Atoms and Molecules |url=https://link.aps.org/doi/10.1103/PhysRev.28.1049 |journal=Physical Review |language=en |volume=28 |issue=6 |pages=1049–1070 |bibcode=1926PhRv...28.1049S |doi=10.1103/PhysRev.28.1049 |issn=0031-899X|url-access=subscription }}</ref> now called the [[Schrödinger equation]], wave mechanics or more commonly in contemporary usage [[quantum mechanics]]. While it was not so easy to solve the mathematics in the early days, fairly rapidly ideas such as the [[chemical bond]] terminology of [[Linus Pauling]]<ref>{{Cite book |last=Pauling |first=Linus |title=The nature of the chemical bond and the structure of molecules and crystals: an introduction to modern structural chemistry |date=2010 |publisher=Cornell Univ. Press |isbn=978-0-8014-0333-0 |edition=3. ed., 17. print |location=Ithaca, NY}}</ref> as well as [[electronic band structure]] concepts were developed.<ref name=":0">{{Cite book |last1=Ashcroft |first1=Neil W. |title=Solid state physics |last2=Mermin |first2=N. David |date=1976 |publisher=Saunders college publ |isbn=978-0-03-083993-1 |location=Fort Worth Philadelphia San Diego [etc.]}}</ref>{{Band structure filling diagram}}From this the concept of nonmetals as "not-a-metal" originates. The original approach to describe metals and nonmetals was a band-structure with [[delocalized electron]]s (i.e. spread out in space). A nonmetal has a [[Band gap|gap]] in the [[Band structure|energy levels]] of the electrons at the [[Fermi level]].<ref name=":0" />{{Rp|location=Chpt 8 & 19}} In contrast, a metal would have at least one  partially occupied band at the Fermi level;<ref name=":0" /> in a semiconductor or insulator there are no delocalized states at the Fermi level, see for instance [[Ashcroft and Mermin]].<ref name=":0" /> (A [[semimetal]] is similar to a metal, with a slightly more complex band structure.) These definitions are equivalent to stating that metals conduct electricity at [[absolute zero]], as suggested by [[Nevill Francis Mott]],<ref name=":3">{{Cite book |last=Yonezawa |first=Fumiko |title=Physics of metal-nonmetal transitions |date=2017 |publisher=IOS Press |isbn=978-1-61499-786-3 |location=Washington, DC |pages= |quote=}}</ref>{{Rp|page=257}} and the equivalent definition at other temperatures is also commonly used as in textbooks such as ''Chemistry of the Non-Metals'' by [[Ralf Steudel]]<ref>{{Cite book |last=Steudel |first=Ralf |url=https://www.degruyter.com/document/doi/10.1515/9783110578065/html |title=Chemistry of the Non-Metals: Syntheses - Structures - Bonding - Applications |date=2020 |publisher=De Gruyter |isbn=978-3-11-057806-5 |page=154 |doi=10.1515/9783110578065}}</ref> and work on [[metal–insulator transition]]s.<ref>{{Cite journal |last=MOTT |first=N. F. |date=1968-10-01 |title=Metal-Insulator Transition |url=https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.40.677 |journal=Reviews of Modern Physics |volume=40 |issue=4 |pages=677–683 |doi=10.1103/RevModPhys.40.677|bibcode=1968RvMP...40..677M |url-access=subscription }}</ref><ref>{{Cite journal |last1=Imada |first1=Masatoshi |last2=Fujimori |first2=Atsushi |last3=Tokura |first3=Yoshinori |date=1998-10-01 |title=Metal-insulator transitions |url=https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.70.1039 |journal=Reviews of Modern Physics |volume=70 |issue=4 |pages=1039–1263 |doi=10.1103/RevModPhys.70.1039|bibcode=1998RvMP...70.1039I |url-access=subscription }}</ref>

Originally<ref>{{Cite journal |last1=Wilson |first1=A. H. |date=1931 |title=The theory of electronic semi-conductors |journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character |language=en |volume=133 |issue=822 |pages=458–491 |bibcode=1931RSPSA.133..458W |doi=10.1098/rspa.1931.0162 |issn=0950-1207 |doi-access=free}}</ref><ref>{{Cite journal |last1=Wilson |first1=A. H. |date=1931 |title=The theory of electronic semi-conductors. - II |journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character |language=en |volume=134 |issue=823 |pages=277–287 |bibcode=1931RSPSA.134..277W |doi=10.1098/rspa.1931.0196 |issn=0950-1207 |doi-access=free}}</ref> this band structure interpretation was based upon a single-electron approach with the Fermi level in the band gap as illustrated in the Figure, not including a complete picture of the [[many-body problem]] where both [[Exchange interaction|exchange]] and [[Electronic correlation|correlation]] terms matter, as well as [[relativistic effect]]s such as [[spin-orbit coupling]]. For instance, the passivity of gold is typically associated with relativistic terms.<ref>{{Cite journal |last=Pyykkö |first=Pekka |date=2012-05-05 |title=Relativistic Effects in Chemistry: More Common Than You Thought |url=https://www.annualreviews.org/content/journals/10.1146/annurev-physchem-032511-143755 |journal=Annual Review of Physical Chemistry |language=en |volume=63 |issue=1 |pages=45–64 |doi=10.1146/annurev-physchem-032511-143755 |pmid=22404585 |bibcode=2012ARPC...63...45P |issn=0066-426X|url-access=subscription }}</ref> A key addition by Mott and [[Rudolf Peierls]] was that these could not be ignored.<ref>{{Cite journal |last1=Mott |first1=N F |last2=Peierls |first2=R |date=1937 |title=Discussion of the paper by de Boer and Verwey |url=https://iopscience.iop.org/article/10.1088/0959-5309/49/4S/308 |journal=Proceedings of the Physical Society |volume=49 |issue=4S |pages=72–73 |bibcode=1937PPS....49...72M |doi=10.1088/0959-5309/49/4S/308 |issn=0959-5309|url-access=subscription }}</ref> For instance, [[Nickel(II) oxide|nickel oxide]] would be a metal if a single-electron approach was used, but in fact has quite a large band gap.<ref>{{Cite journal |last1=Boer |first1=J H de |last2=Verwey |first2=E J W |date=1937 |title=Semi-conductors with partially and with completely filled 3 d -lattice bands |url=https://iopscience.iop.org/article/10.1088/0959-5309/49/4S/307 |journal=Proceedings of the Physical Society |volume=49 |issue=4S |pages=59–71 |bibcode=1937PPS....49...59B |doi=10.1088/0959-5309/49/4S/307 |issn=0959-5309|url-access=subscription }}</ref> As of 2024 it is more common to use an approach based upon [[density functional theory]] where the many-body terms are included.<ref>{{Cite web |last=Burke |first=Kieron |date=2007 |title=The ABC of DFT |url=https://dft.uci.edu/doc/g1.pdf}}</ref><ref>{{Cite book |last1=Gross |first1=Eberhard K. U. |url=https://books.google.com/books?id=aG4ECAAAQBAJ&q=density+functional+theory |title=Density Functional Theory |last2=Dreizler |first2=Reiner M. |date=2013 |publisher=Springer Science & Business Media |isbn=978-1-4757-9975-0 |language=en}}</ref>  Although accurate calculations remain a challenge, reasonable results are now available in many cases.<ref>{{Cite journal |last1=Ferreira |first1=Luiz G. |last2=Marques |first2=Marcelo |last3=Teles |first3=Lara K. |date=2008 |title=Approximation to density functional theory for the calculation of band gaps of semiconductors |url=https://link.aps.org/doi/10.1103/PhysRevB.78.125116 |journal=Physical Review B |language=en |volume=78 |issue=12 |article-number=125116 |arxiv=0808.0729 |bibcode=2008PhRvB..78l5116F |doi=10.1103/PhysRevB.78.125116 |issn=1098-0121}}</ref><ref>{{Cite journal |last1=Tran |first1=Fabien |last2=Blaha |first2=Peter |date=2017 |title=Importance of the Kinetic Energy Density for Band Gap Calculations in Solids with Density Functional Theory |journal=The Journal of Physical Chemistry A |language=en |volume=121 |issue=17 |pages=3318–3325 |bibcode=2017JPCA..121.3318T |doi=10.1021/acs.jpca.7b02882 |issn=1089-5639 |pmc=5423078 |pmid=28402113}}</ref>

It is common to nuance the early definition of [[Alan Herries Wilson]] and Mott which was for a  zero temperature. As discussed by [[Peter Edwards (chemist)|Peter Edwards]] and colleagues,<ref>{{Cite journal |last1=Edwards |first1=P. P. |last2=Lodge |first2=M. T. J. |last3=Hensel |first3=F. |last4=Redmer |first4=R. |date=2010 |title='… a metal conducts and a non-metal doesn't' |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |language=en |volume=368 |issue=1914 |pages=941–965 |bibcode=2010RSPTA.368..941E |doi=10.1098/rsta.2009.0282 |issn=1364-503X |pmc=3263814 |pmid=20123742}}</ref> as well as [[Fumiko Yonezawa]],<ref name=":3" />{{Rp|pages=257–261}}it is important to consider the temperatures at which both metals and nonmetals are used. Yonezawa provides a general definition for both general temperatures and conditions (such as standard temperature and pressure):<ref name=":3" />{{Rp|page=260}}

{{blockquote|text=When a material conducts and at the same time the temperature coefficient of the electric conductivity of that material is not positive under a certain environmental condition, the material is metallic under that environmental condition. A material which does not satisfy these requirements is not metallic under that environmental condition.}}

The precise meaning of semiconductor needs a little care. In terms of the temperature dependence of their conductivity they are all classified as insulators; the pure forms are [[intrinsic semiconductor]]s. When they are doped their conductivity continues to increase with temperature,<ref name=":0" /> and can become substantial; hence the ambiguities with an empirical categorisation using conductivity described earlier. Indeed, some elements that are normally considered as insulators have been exploited as semiconductors. For instance diamond, which has the largest band gap of the elements that are solids under normal conditions,<ref>{{Cite journal |last1=Strehlow |first1=W. H. |last2=Cook |first2=E. L. |date=1973-01-01 |title=Compilation of Energy Band Gaps in Elemental and Binary Compound Semiconductors and Insulators |url=https://pubs.aip.org/aip/jpr/article-abstract/2/1/163/241551/Compilation-of-Energy-Band-Gaps-in-Elemental-and?redirectedFrom=fulltext |journal=Journal of Physical and Chemical Reference Data |volume=2 |issue=1 |pages=163–200 |doi=10.1063/1.3253115 |bibcode=1973JPCRD...2..163S |issn=0047-2689|url-access=subscription }}</ref> has a number of semiconductor applications.<ref>{{Cite journal |last=Collins |first=Alan T. |date=1997 |title=The optical and electronic properties of semiconducting diamond |url=https://royalsocietypublishing.org/doi/10.1098/rsta.1993.0017 |journal=Philosophical Transactions of the Royal Society of London, Series A |volume=342 |issue=1664 |pages=233–244 |doi=10.1098/rsta.1993.0017|url-access=subscription }}</ref><ref>{{Cite journal |last=Umezawa |first=Hitoshi |date=2018-05-01 |title=Recent advances in diamond power semiconductor devices |url=https://linkinghub.elsevier.com/retrieve/pii/S1369800117322217 |journal=Materials Science in Semiconductor Processing |series=Wide band gap semiconductors technology for next generation of energy efficient power electronics |volume=78 |pages=147–156 |doi=10.1016/j.mssp.2018.01.007 |issn=1369-8001|url-access=subscription }}</ref>

Band structure definitions of metals and nonmetals are widely used in current research into materials, and apply both to single elements such as insulating boron<ref>{{Cite journal |last1=Ogitsu |first1=Tadashi |last2=Schwegler |first2=Eric |last3=Galli |first3=Giulia |date=2013 |title=β-Rhombohedral Boron: At the Crossroads of the Chemistry of Boron and the Physics of Frustration |url=https://pubs.acs.org/doi/10.1021/cr300356t |journal=Chemical Reviews |language=en |volume=113 |issue=5 |pages=3425–3449 |doi=10.1021/cr300356t |issn=0009-2665 |osti=1227014 |pmid=23472640}}</ref> as well as compounds such as [[strontium titanate]].<ref>{{Cite journal |last1=Reihl |first1=B. |last2=Bednorz |first2=J. G. |last3=Müller |first3=K. A. |last4=Jugnet |first4=Y. |last5=Landgren |first5=G. |last6=Morar |first6=J. F. |date=1984 |title=Electronic structure of strontium titanate |url=https://link.aps.org/doi/10.1103/PhysRevB.30.803 |journal=Physical Review B |language=en |volume=30 |issue=2 |pages=803–806 |bibcode=1984PhRvB..30..803R |doi=10.1103/PhysRevB.30.803 |issn=0163-1829|url-access=subscription }}</ref> The characteristics associated with metals and nonmetals in early work such as their appearance and mechanical properties are now understood to be consequences of how the atoms and electrons are arranged.

==Comparison of selected properties==
The two tables in this section list some of the properties of five types of elements (noble gases, halogen nonmetals, unclassified nonmetals, metalloids and, for comparison, metals) based on their most stable forms at standard temperature and pressure. The dashed lines around the columns for metalloids signify that the treatment of these elements as a distinct type can vary depending on the author, or classification scheme in use.

=== Physical properties by element type ===
{{hatnote|See also {{slink||Physical}} }}

[[Physical property|Physical properties]] are listed in loose order of ease of their determination.

{|class="wikitable" style="font-size:95%"
|-
!rowspan="2" style="horizontal=align:center; font-size:105%""|Property
!colspan="5" style="horizontal=align:center; font-size:105%""|Element type
|-
! scope="col" style="width:17%; text-align:left"|Metals
! scope="col" style="width:17%; border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD; border-top:2px dashed #CDCDCD; text-align:left"|Metalloids
! scope="col" style="width:17%; text-align:left|Unc. nonmetals
! scope="col" style="width:17%; text-align:left"|Halogen nonmetals
! scope="col" style="width:17%; text-align:left"|Noble gases
|- style="vertical-align:top"
| scope="row" |General physical appearance
| lustrous<ref name="Kneen"/>
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD|lustrous<ref name="Rochow 1966, p. 4">[[#Rochow1966|Rochow 1966, p. 4]]</ref>
| {{indented plainlist|indent=0.9em|
* ◇ lustrous: carbon, phosphorus, selenium<ref>[[#Wiberg|Wiberg 2001, p. 780]]; [[#Emsley2011|Emsley 2011, p. 397]]; [[#Rochow1966|Rochow 1966, pp. 23, 84]]</ref>
* ◇ colored: sulfur<ref>[[#Kneen|Kneen, Rogers & Simpson 1972, p. 439]]</ref>
* ◇ colorless: hydrogen, nitrogen, oxygen<ref>[[#Kneen|Kneen, Rogers & Simpson 1972, pp. 321, 404, 436]]</ref>}}
| {{indented plainlist|indent=0.9em|
* ◇ lustrous: iodine<ref name="Vernon2013"/>
* ◇ colored: fluorine, chlorine, bromine<ref>[[#Kneen|Kneen, Rogers & Simpson 1972, p. 465]]</ref>}}
| colorless<ref>[[#Kneen|Kneen, Rogers & Simpson 1972, p. 308]]</ref>
|- style="vertical-align:top"
| scope="row" rowspan=3|Form and density<ref>[[#Tregarthen|Tregarthen 2003, p. 10]]</ref>
| solid <br />(Hg liquid)
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD| solid
| solid or gas
| solid or gas <br />(bromine liquid)
| gas
|- style="vertical-align:top"
|often [[Heavy metals|high density]] such as iron, lead, tungsten
|style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD|low to moderately high density
|low density
|rowspan=2| low density
|low density
|- style="vertical-align:top"
|some [[light metals]] including beryllium, magnesium, aluminium
|style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD|all lighter than iron
|hydrogen, nitrogen lighter than air<ref>[[#Lewis|Lewis 1993, pp. 28, 827]]</ref>
|helium, neon lighter than air<ref>[[#Lewis|Lewis 1993, pp. 28, 813]]</ref>
|- style="vertical-align:top"
| scope="row" | [[Plasticity (physics)|Plasticity]]
| mostly malleable and ductile<ref name="Kneen"/>
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD|often brittle<ref name="Rochow 1966, p. 4" />
| phosphorus, sulfur, selenium, brittle{{efn|All four have less stable non-brittle forms: carbon as [[Graphite#Expanded graphite|exfoliated (expanded) graphite]],<ref name="Chung">[[#Chung|Chung 1987]]</ref><ref>[[#Godfrin|Godfrin & Lauter 1995, pp. 216‒218]]</ref> and as [[carbon nanotube]] wire;<ref name="Janas">[[#Janas|Janas, Cabrero-Vilatela & Bulmer 2013]]</ref> phosphorus as white phosphorus (soft as wax, pliable and can be cut with a knife, at room temperature);<ref name="Holderness 1979, p. 255" /> sulfur as plastic sulfur;<ref name="ReferenceE" /> and selenium as selenium wires.<ref name="ReferenceF" />}}
| iodine brittle<ref>[[#Wiberg|Wiberg 2001, p. 416]]</ref>
| not applicable
|- style="vertical-align:top"
| scope="row" |[[Electrical resistivity and conductivity|Electrical conductivity]]
| good{{efn|Metals have electrical conductivity values of from {{val|6.9|e=3|u=S•cm<sup>−1</sup>}} for [[manganese]] to {{val|6.3|e=5}} for [[silver]].<ref>[[#Desai|Desai, James & Ho 1984, p. 1160]]; [[#Matula|Matula 1979, p. 1260]]</ref>}}
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD|{{indented plainlist|indent=0.9em|
* ◇ moderate: boron, silicon, germanium, tellurium
* ◇ good: arsenic, antimony{{efn|Metalloids have electrical conductivity values of from {{val|1.5|e=-6|u=S•cm<sup>−1</sup>}} for boron to {{val|3.9|e=4}} for [[arsenic]].<ref>[[#Schaefer|Schaefer 1968, p. 76]]; [[#Carapella|Carapella 1968, pp. 29‒32]]</ref>}}
  }}
| {{indented plainlist|indent=0.9em|
* ◇ poor: hydrogen, nitrogen, oxygen, sulfur
* ◇ moderate: phosphorus, selenium
* ◇ good: carbon{{efn|Unclassified nonmetals have electrical conductivity values of from ca. {{val|1|e=−18|u=S•cm<sup>−1</sup>}} for the elemental gases to {{val|3|e=4}} in graphite.<ref name="Bog">[[#Bogoroditskii1967|Bogoroditskii & Pasynkov 1967, p. 77]]; [[#Jenkins|Jenkins & Kawamura 1976, p. 88]]</ref>}}
  }}
| {{indented plainlist|indent=0.9em|
* ◇ poor: fluorine, chlorine, bromine
* ◇ moderate: I{{efn|Halogen nonmetals have electrical conductivity values of from ca. {{val|1|e=-18|u=S•cm<sup>−1</sup>}} for {{abbr|F|fluorine}} and {{abbr|Cl|chlorine}} to {{val|1.7|e=-8|u=S•cm<sup>−1</sup>}} for iodine.<ref name="Bog"/><ref name="Greenwood 2002, p. 804">[[#Greenwood|Greenwood & Earnshaw 2002, p. 804]]</ref>}}
  }}
| poor{{efn|Elemental gases have electrical conductivity values of ca. {{val|1|e=−18|u=S•cm<sup>−1</sup>}}.<ref name="Bog"/>}}
|- style="vertical-align:top"
| scope="row" |[[Electronic band structure|Electronic structure]]<ref name="K&W">[[#Keeler|Keeler & Wothers 2013, p. 293]]</ref>
| metal (beryllium, strontium, α-tin, ytterbium, bismuth are semimetals)
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD; border-bottom:2px dashed #CDCDCD"| semimetal (arsenic, antimony) or semiconductor
| {{indented plainlist|indent=0.9em|
* ◇ semimetal: carbon
* ◇ semiconductor: phosphorus
* ◇ insulator: hydrogen, nitrogen, oxygen, sulfur
  }}
| semiconductor ({{abbr|I|iodine}}) or insulator
| insulator
|}

=== Chemical properties by element type ===
{{hatnote|See also {{slink||Chemical}}}}

[[Chemical properties]] are listed from general characteristics to more specific details.

{|class="wikitable" style="font-size:95%"
|-
!rowspan="2" style="horizontal=align:center; font-size:105%""|Property
!colspan="5" style="horizontal=align:center; font-size:105%""|Element type
|-
! scope="col" style="width:17%; text-align:left"|Metals
! scope="col" style="width:17%; text-align:left; border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD; border-top:2px dashed #CDCDCD"|Metalloids
! scope="col" style="width:17%; text-align:left" | Unc. nonmetals
! scope="col" style="width:17%; text-align:left"|Halogen nonmetals
! scope="col" style="width:17%; text-align:left"|Noble gases
|- style="vertical-align:top"
| scope="row" |General chemical behavior
| {{indented plainlist|indent=0.9em|
* ◇ strong to weakly metallic<ref>[[#Kneen|Kneen, Rogers & Simpson 1972, p. 264]]</ref>
* ◇ [[noble metal]]s are relatively inert<ref>[[#Rayner|Rayner-Canham 2018, p. 203]]</ref>
  }}
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD|weakly nonmetallic{{efn|Metalloids always give "compounds less acidic in character than the corresponding compounds of the [typical] nonmetals."<ref name="Rochow 1966, p. 4" />}}
| moderately nonmetallic<ref name="W2009">[[#Welcher|Welcher 2009, p. 3–32]]: "The elements change from{{nbsp}}... metalloids, to moderately active nonmetals, to very active nonmetals, and to a noble gas."</ref>
| strongly nonmetallic<ref>[[#Mackin|Mackin 2014, p. 80]]</ref>
| {{indented plainlist|indent=0.9em|
* ◇ inert to nonmetallic<ref>[[#Johnson1966|Johnson 1966, pp. 105–108]]</ref>
* ◇ radon shows some cationic behavior<ref>[[#Stein1969|Stein 1969, pp. 5396‒5397]]; [[#Pitzer|Pitzer 1975, pp. 760‒761]]</ref>
  }}
|- style="vertical-align:top"
| scope="row" rowspan=3|[[Oxide]]s
|basic; some [[amphoteric]] or acidic<ref name="Porterfield">[[#Porter|Porterfield 1993, p. 336]]</ref>
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"|amphoteric or weakly acidic<ref>[[#Rochow1966|Rochow 1966, p. 4]]; [[#Atkins2006|Atkins et al. 2006, pp. 8, 122–123]]</ref>{{efn|Arsenic trioxide reacts with sulfur trioxide, forming [[arsenic sulfate|arsenic "sulfate"]] As<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>.<ref>[[#Wiberg|Wiberg 2001, p. 750]].</ref> This substance is covalent in nature rather than ionic;<ref>[[#Douglade|Douglade & Mercier 1982, p. 723]]</ref> it is also given as As<sub>2</sub>O<sub>3</sub>·3SO<sub>3</sub>.<ref>[[#Gillespie|Gillespie & Robinson 1959, p. 418]]</ref>}}
|acidic{{efn|{{chem|||NO|2}}, {{chem|||N|2||O|5}}, {{chem|||SO|3}}, {{chem|||SeO|3}} are strongly acidic.<ref>[[#Sanderson1967|Sanderson 1967, p. 172]]; [[#Mingos2019|Mingos 2019, p. 27]]</ref>}} or neutral{{efn|H<sub>2</sub>O, CO, NO, N<sub>2</sub>O are neutral oxides; CO and N<sub>2</sub>O are "formally the [[anhydride]]s of [[formic acid|formic]] and [[hyponitrous acid]], respectively viz. CO + H<sub>2</sub>O → H<sub>2</sub>CO<sub>2</sub> (HCOOH, formic acid); N<sub>2</sub>O + H<sub>2</sub>O → H<sub>2</sub>N<sub>2</sub>O<sub>2</sub> (hyponitrous acid)."<ref>[[#House|House 2008, p. 441]]</ref>}}

|acidic{{efn|{{chem|||ClO|2}}, {{chem|||Cl|2||O|7}}, {{chem|||I|2||O|5}} are strongly acidic.<ref>[[#Mingos2019|Mingos 2019, p. 27]]; [[#Sanderson1967|Sanderson 1967, p. 172]]</ref>}}

|metastable XeO<sub>3</sub> is acidic;<ref>[[#Wiberg|Wiberg 2001, p. 399]]</ref> stable XeO<sub>4</sub> strongly so<ref>[[#Klae|Kläning & Appelman 1988, p. 3760]]</ref>
|- style="vertical-align:top"
| few glass formers{{efn|Metals that form glasses are: vanadium; molybdenum, tungsten; alumnium, indium, thallium; tin, lead; and bismuth.<ref name="Rao 2002, p. 22">[[#Rao2002|Rao 2002, p. 22]]</ref>}}
|style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"|all glass formers<ref>[[#Sidorov|Sidorov 1960, pp. 599–603]]</ref>
|some glass formers{{efn|Unclassified nonmetals that form glasses are phosphorus, sulfur, selenium;<ref name="Rao 2002, p. 22"/> [[carbon dioxide|CO<sub>2</sub>]] forms a glass at 40&nbsp;GPa.<ref>[[#McMillan|McMillan 2006, p. 823]]</ref>}}
|no glass formers reported
|no glass formers reported
|- style="vertical-align:top"
|ionic, polymeric, layer, chain, and molecular structures<ref>[[#Wells|Wells 1984, p. 534]]</ref>
|style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"|polymeric in structure<ref name="Pudd">[[#Puddephatt|Puddephatt & Monaghan 1989, p. 59]]</ref>
|{{indented plainlist|indent=0.9em|
* ◇ mostly molecular<ref name="Pudd"/>
* ◇ carbon, phosphorus, sulfur, selenium have 1+ polymeric forms}}

|{{indented plainlist|indent=0.9em|
* ◇ mostly molecular
* ◇ iodine has a polymeric form, [[Iodine pentoxide|I<sub>2</sub>O<sub>5</sub>]]<ref>[[#King1995|King 1995, p. 182]]</ref>}}

|{{indented plainlist|indent=0.9em|
* ◇ mostly molecular
* ◇ [[xenon dioxide|XeO<sub>2</sub>]] is polymeric<ref>[[#Ritter|Ritter 2011, p. 10]]</ref>}}
|- style="vertical-align:top"
| scope="row" |Compounds with metals
| alloys<ref name="Kneen"/> or [[intermetallic compound]]s<ref>[[#Yama|Yamaguchi & Shirai 1996, p. 3]]</ref>
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"|tend to form alloys or intermetallic compounds<ref>[[#Vernon2020|Vernon 2020, p. 223]]</ref>
| {{indented plainlist|indent=0.9em|
* ◇ salt-like to covalent or metallic: hydrogen†, carbon, nitrogen, phosphorus, sulfur, selenium<ref name="Vernon2020p220"/>
* ◇ mainly ionic: oxygen<ref>[[#Woodward|Woodward et al. 1999, p. 134]]</ref>
  }}
| mainly ionic<ref name="Cotton"/>
| simple compounds at STP not known{{efn|[[Disodium helide]] (Na<sub>2</sub>He) is a compound of helium and sodium that is stable at high pressures above 113&nbsp;GPa. Argon forms an alloy with nickel, at 140&nbsp;GPa and close to 1,500 K, however at this pressure argon is no longer a noble gas.<ref>[[#Dalton|Dalton 2019]]</ref>}}
|- style="vertical-align:top"
| scope="row" rowspan=3|[[Ionization energy]] (kJ mol<sup>−1</sup>)<ref name="AylwardIE">[[#Aylward|Aylward & Findlay 2008, p. 132]]</ref>&thinsp;‡
| low to high
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"|moderate
| moderate to high
| high
| high to very high
|- style="vertical-align:top"
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"| 376 to 1,007
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"| 762 to 947
| 941 to 1,402
| 1,008 to 1,681
| 1,037 to 2,372
|- style="vertical-align:top"
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"| average 643
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"| average 833
| average 1,152
| average 1,270
| average 1,589
|- style="vertical-align:top"
| scope="row" rowspan=3|[[Electronegativity]] (Pauling){{efn|Values for the noble gases are from Rahm, Zeng and Hoffmann.<ref name="Rahm">[[#Rahm|Rahm, Zeng & Hoffmann 2019, p. 345]]</ref>}}<ref name="AylwardEN">[[#Aylward|Aylward & Findlay 2008, p. 126]]</ref>&thinsp;‡
| low to high
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"| moderate
| moderate to high
| high
| high (radon) to very high
|- style="vertical-align:top"
| 0.7 to 2.54
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD"| 1.9 to 2.18
| 2.19 to 3.44
| 2.66 to 3.98
| ca. 2.43 to 4.7
|- style="vertical-align:top"
| average 1.5
| style="border-right:2px dashed #CDCDCD; border-left:2px dashed #CDCDCD; border-bottom:2px dashed #CDCDCD;"| average 2.05
| average 2.65
| average 3.19
| average 3.3
|}
<span style="font-size:95%">
† Hydrogen can also form alloy-like hydrides<ref name="Cao4"/><br />
‡ The labels ''low'', ''moderate'', ''high'', and ''very high'' are arbitrarily based on the value spans listed in the table</span>

==See also==
* [[CHON]] (carbon, hydrogen, oxygen, nitrogen)
* [[List of nonmetal monographs]]
* [[Metallization pressure]]
* [[Nonmetal (astrophysics)]]
* [[Period 1]] elements (hydrogen & helium)
* [[Properties of nonmetals (and metalloids) by group]]
{{Clear}}

==Notes==
{{notelist|colwidth=45em}}

==References==
===Citations===
{{Reflist|20em}}

===Bibliography===

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=======================

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{{refend}}

==External links==
* {{Commons category-inline|Nonmetals}}
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[[Category:Nonmetals]]
[[Category:Periodic table]]