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{{Short description|Related chemical elements of the periodic table}}
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{{Infobox periodic table group
| title       = Boron&nbsp;group (group&nbsp;13)
| group number= 13
| trivial name= triels
| by element  = boron group
| CAS         = IIIA
| old IUPAC   = IIIB
| mark        = B,Al,Ga,In,Tl,Nh
| left        = [[Group 12 element|group 12]]
| right       = [[carbon group]]
}}
{| class="floatright"
! colspan=2 style="text-align:left;" | ↓&nbsp;<small>[[Period (periodic table)|Period]]</small>
|-
! [[Period 2 element|2]]
| {{element cell image|5|Boron|B| |Solid|Metalloid|Primordial|image=Bor 1.jpg|image caption=Boron chunks}}
|-
! [[Period 3 element|3]]
| {{element cell image|13|Aluminium|Al| |Solid|Other metal|Primordial|image=Aluminium-4.jpg|image caption=Aluminium metal}}
|-
! [[Period 4 element|4]]
| {{element cell image|31|Gallium|Ga| |Solid|Other metal|Primordial|image=Gallium crystals.jpg|image caption=Gallium crystals}}
|-
! [[Period 5 element|5]]
| {{element cell image|49|Indium|In| |Solid|Other metal|Primordial|image=Indium wire.jpg|image caption=Ductile indium wire}}
|-
! [[Period 6 element|6]]
| {{element cell image|81|Thallium|Tl| |Solid|Other metal|Primordial|image=Thallium pieces in ampoule.jpg|image caption=Thallium pieces stored in a glass ampoule under argon atmosphere}}
|-
! [[Period 7 element|7]]
| {{element cell image|113|Nihonium|Nh| |Unknown phase|Other metal|Synthetic|legend=other metal}}
|-
| colspan="2"|
----
''Legend''
{| style="text-align:center; border:0; margin:1em auto;"
|-
| style="border:{{element color|Primordial}}; background:{{Element color|table mark}}; padding:0 2px;" | [[primordial element]]
|-
| style="border:{{element color|Synthetic}}; background:{{Element color|table mark}};" | [[synthetic element]]
|}
|}

The '''boron group''' are the [[chemical element]]s in '''[[periodic table group|group 13]]''' of the [[periodic table]], consisting of [[boron]] (B), [[aluminium]] (Al), [[gallium]] (Ga), [[indium]] (In), [[thallium]] (Tl) and [[nihonium]] (Nh). This group lies in the [[p-block]] of the periodic table. The elements in the boron group are characterized by having three [[valence electron]]s.<ref name="C. Kotz, Treichel, R. Townsend 2009 351">{{cite book|title = Chemistry and chemical reactivity |author1=Kotz, John C. |author2=Treichel, Paul |author3=Townsend, John Raymond  |name-list-style=amp|publisher = Thomson Books| year = 2009 |location = Belmont, Ca, USA|isbn = 978-0-495-38712-1|volume= 2 | page=351|url=https://books.google.com/books?id=jcn6sgt7RpoC&pg=PA351}}</ref> These elements have also been referred to as the '''triels'''.{{efn|The name '''icosagens''' for group 13 has occasionally been used,<ref>{{Greenwood&Earnshaw2nd|p=227}}</ref> in reference to the [[icosahedron|icosahedral]] structures characteristically formed by its elements.}}

Several group 13 elements have biological roles in the [[ecosystem]]. Boron is a trace element in humans and is essential for some plants. Lack of boron can lead to stunted plant growth, while an excess can also cause harm by inhibiting growth. Aluminium has neither a biological role nor significant toxicity and is considered safe. Indium and gallium can stimulate metabolism;<ref>Pharmacology and Nutritional Intervention in the Treatment of Disease edited by Faik Atroshi, page 45</ref> gallium is credited with the ability to bind itself to iron proteins. Thallium is highly toxic, interfering with the function of numerous vital enzymes, and has seen use as a [[pesticide]].<ref>{{cite book |title=Clinical neurotoxicology: syndromes, substances, environments |last=Dobbs |first=Michael |year=2009 |publisher=Saunders |pages=276–278 |location=Philadelphia, Pa |url=https://books.google.com/books?id=Pmcy24y2HyMC&pg=PA277|isbn=978-0-323-05260-3}}</ref>

==Characteristics==
Like other groups, the members of this family show patterns in [[electron configuration]], especially in the outermost shells, resulting in trends in chemical behavior:

{| class="wikitable" style="white-space:nowrap;"
|-
!''[[Atomic number|Z]]'' !! [[Chemical element|Element]] !! Electrons per [[Electron shell|shell]]
|-
| 5 || boron || 2, 3
|-
| 13 || aluminium || 2, 8, 3
|-
| 31 || gallium || 2, 8, 18, 3
|-
| 49 || indium || 2, 8, 18, 18, 3
|-
| 81 || thallium || 2, 8, 18, 32, 18, 3
|-
| 113 || nihonium || 2, 8, 18, 32, 32, 18, 3<br/>(predicted)
|}

The boron group is notable for trends in the electron configuration, as shown above, and in some of its elements' characteristics. An example of a trend in reactivity is boron's tendency to form reactive compounds with hydrogen.<ref name="Harding, A. Johnson, Janes 2002 113">{{cite book |title=Elements of the p block |last1=Harding, A. |last2=Johnson |last3=Janes |first1=Charlie |first2=David |first3=Rob |year=2002|publisher=The Open University |location=Cambridge, UK |isbn=0-85404-690-9|page=113 |url=https://books.google.com/books?id=W0HW8wgmQQsC&pg=PA113}}</ref> However, boron differs from the other group members. It has the second highest [[hardness]] of all the elements, only exceeded by [[diamond]].<ref name=Sicius-2024>{{Cite book |last=Sicius |first=Hermann |url=https://link.springer.com/10.1007/978-3-662-68921-9 |title=Handbook of the Chemical Elements |date=2024 |publisher=Springer Berlin Heidelberg |isbn=978-3-662-68920-2 |location=Berlin, Heidelberg |language=en |doi=10.1007/978-3-662-68921-9}}</ref>{{rp|145}} Boron is considered a semi-metal while the others in the group are metals.<ref name=Sicius-2024/>{{rp|141}} Boron's melting point at  2076&nbsp;°C is much higher than the second highest in the group, aluminium, at 660&nbsp;°C.<ref name=Sicius-2024/>{{rp|143}}

===Chemical reactivity===

====Hydrides====
Most of the elements in the boron group show increasing [[reactivity (chemistry)|reactivity]] as the elements get heavier in atomic mass and higher in atomic number. [[Boron]], the first element in the group, is generally unreactive with many elements except at high temperatures, although it is capable of forming many compounds with [[hydrogen]], sometimes called ''[[boranes]]''.<ref>{{cite book |title=Concepts And Problems In Inorganic Chemistry  |author=Raghavan, P. S.  |year=1998 |publisher=Discovery Publishing House |location=New Delhi, India|isbn=81-7141-418-4 |page=43 |url=https://books.google.com/books?id=pBiS0jc-kWIC&pg=PA43}}</ref> The simplest borane is [[diborane]], or B<sub>2</sub>H<sub>6</sub>.<ref name="Harding, A. Johnson, Janes 2002 113"/> Another example is B<sub>10</sub>H<sub>14</sub>.

The next group-13 elements, [[aluminium]] and [[gallium]], form fewer stable hydrides, although both AlH<sub>3</sub> and GaH<sub>3</sub> exist. Indium, the next element in the group, is not known to form many hydrides, except in complex compounds such as the [[phosphine]] complex {{chem2|H3InP(Cy)3}} (Cy=[[cyclohexyl]]).<ref>{{Cite journal | last1 = Cole | first1 = M. L. | last2 = Hibbs | first2 = D. E. | last3 = Jones | first3 = C. | last4 = Smithies | first4 = N. A. | title = Phosphine and phosphido indium hydride complexes and their use in inorganic synthesis | doi = 10.1039/A908418E | journal = Journal of the Chemical Society, Dalton Transactions | issue = 4 | pages = 545–550 | year = 2000 }}</ref> No stable compound of thallium and hydrogen has been synthesized in any laboratory.

{| class="wikitable collapsible collapsed"
 ! colspan="6"| Some common chemical compounds of the boron group<ref name="Harding, A. Johnson, Janes 2002 113"/>
<ref name="grp.13 elem. chem.">[[#Downs1993|Downs]], pp. 197–201</ref><ref>{{cite book |title= Oxford dictionary of chemistry |last= Daintith|first= John|year= 2004|publisher= Market House Books|url= https://books.google.com/books?id=jzT-zlKESmsC&pg=PA269|isbn= 978-0-19-860918-6}}</ref><ref name="In2">{{cite book| script-title=ru:Химия индия|author1=Bleshinsky, S. V. |author2=Abramova, V. F. |publisher = Frunze|page=301|year =1958|language=ru}}</ref><ref>[[#Downs1993|Downs]], pp. 195–196</ref><ref>[[#Henderson|Henderson]], p. 6</ref>
|-
! Element!!Oxides!!Hydrides!!Fluorides!!Chlorides!!Sulfides
|- valign="top"
| rowspan=9 | [[Boron]]
|(β/g/α)B<sub>2</sub>O<sub>3</sub> || B<sub>2</sub>H<sub>6</sub> || BF<sub>3</sub> || BCl<sub>3</sub> || B<sub>2</sub>S<sub>3</sub>
|-
|B<sub>2</sub>O || B<sub>10</sub>H<sub>14</sub> || {{chem|BF|4|-}} ||  ||
|-
|B<sub>6</sub>O || BH<sub>3</sub> || B<sub>2</sub>F<sub>4</sub> ||  ||
|-
| || B<sub>5</sub>H<sub>9</sub> || BF ||  ||
|-
| || B<sub>6</sub>H<sub>12</sub> ||  ||  ||
|-
| || B<sub>4</sub>H<sub>10</sub> ||  ||  ||
|-
| || B{{su|b=6}}{{chem|H|6|2-}} ||  ||  ||
|-
| ||  B{{su|b=12}}{{chem|H|12|2-}} ||  ||  ||
|-
| || B<sub>20</sub>H<sub>26</sub> ||  ||  ||
|- valign="top"
| rowspan=4 | [[Aluminium]]
| (γ/δ/η/θ/χ)Al<sub>2</sub>O<sub>3</sub>|| (α/α`/β/δ/ε/θ/γ) AlH<sub>3</sub> || AlF<sub>3</sub> || AlCl<sub>3</sub> || (α/β/γ) Al<sub>2</sub>S<sub>3</sub>
|-
|Al<sub>2</sub>O || Al<sub>2</sub>H<sub>6</sub> ||  ||  ||
|-
|AlO || AlH<sub>4</sub> ||  ||  ||
|-
| || {{chem|AlH|4|-}} ||  ||  ||
|- valign="top"
| rowspan=6 | [[Gallium]]
|(α/β/δ/γ/ε) Ga<sub>2</sub>O<sub>3</sub> || Ga<sub>2</sub>H<sub>6</sub> || GaF<sub>3</sub> || GaCl<sub>3</sub> || GaS
|-
| || GaH<sub>4</sub> ||  || GaCl<sub>2</sub> ||
|-
| || GaH<sub>3</sub> ||  || Ga<sub>2</sub>Cl<sub>4</sub> ||
|-
| ||  ||  || Ga<sub>2</sub>Cl<sub>6</sub> ||
|-
| ||  ||  || {{chem|GaCl|4|-}} ||
|-
| ||  ||  || Ga{{su|b=2}}{{chem|Cl|7|-}} ||
|- valign="top"
| rowspan=2 | [[Indium]]
| In<sub>2</sub>O<sub>3</sub> || InH<sub>3</sub> || InF<sub>3</sub> || InCl<sub>3</sub> || (α/β/γ) In<sub>2</sub>S<sub>3</sub>
|-
| In<sub>2</sub>O ||  ||  ||  ||
|- valign="top"
| rowspan=4 | [[Thallium]]
| Tl<sub>2</sub>O<sub>3</sub> || TlH<sub>3</sub> || TlF || TlCl ||
|-
| Tl<sub>2</sub>O || TlH || TlF<sub>3</sub> || TlCl<sub>3</sub> ||
|-
| TlO<sub>2</sub> ||  || {{chem|TlF|4|3-}} || TlCl<sub>2</sub> ||
|-
| Tl<sub>4</sub>O<sub>3</sub> ||  || {{chem|TlF|3|2-}} || Tl<sub>2</sub>Cl<sub>3</sub> ||
|- valign="top"
| rowspan=2 | [[Nihonium]]
| (Nh<sub>2</sub>O){{efn|To this date, no nihonium compounds have been synthesized (except possibly NhOH), and all other proposed compounds are entirely theoretical.}}
 ||(NhH)  || (NhF) || (NhCl) || NhOH
|-
| (Nh<sub>2</sub>O<sub>3</sub>) ||(NhH<sub>3</sub>)  ||(NhF<sub>3</sub>)  ||(NhCl<sub>3</sub>)  ||
|-
| || || ||({{chem|NhF|6|-}}) || ||
|}

====Oxides====
All of the boron-group elements are known to form a trivalent oxide, with two atoms of the element bonded [[covalent bonds|covalently]] with three atoms of [[oxygen]]. These elements show a trend of increasing [[pH]] (from [[acid]]ic to [[base (chemistry)|basic]]).<ref>{{cite journal|doi=10.1063/1.433959|url=http://cnx.org/content/m32460/latest/?collection=col11124/latest|access-date=June 16, 2011|title=Determinations of structure and bonding in vitreous B<sub>2</sub>O<sub>3</sub> by means of B<sup>10</sup>, B<sup>11</sup>, and O<sup>17</sup> NMR|year=1977|last1=Jellison|first1=G. E.|last2=Panek|first2=L. W.|last3=Bray|first3=P. J.|last4=Rouse|first4=G. B.|journal=The Journal of Chemical Physics|volume=66|issue=2|page=802|bibcode = 1977JChPh..66..802J |url-access=subscription}}</ref> [[Boron trioxide|Boron oxide]] (B<sub>2</sub>O<sub>3</sub>) is slightly acidic, [[aluminium oxide|aluminium]] and [[gallium(III) oxide|gallium oxide]] (Al<sub>2</sub>O<sub>3</sub> and Ga<sub>2</sub>O<sub>3</sub> respectively) are amphoteric, [[indium(III) oxide]] (In<sub>2</sub>O<sub>3</sub>) is nearly amphoteric, and [[thallium(III) oxide]] (Tl<sub>2</sub>O<sub>3</sub>) is a [[Lewis base]] because it dissolves in acids to form salts. Each of these compounds are stable, but thallium oxide [[Thermal decomposition|decomposes]] at temperatures higher than 875&nbsp;°C.

[[Image:B2O3powder.JPG|thumb|right|A powdered sample of [[boron trioxide]] (B<sub>2</sub>O<sub>3</sub>), one of the oxides of boron]]

====Halides====
The elements in group 13 are also capable of forming stable compounds with the [[halogens]], usually with the formula MX<sub>3</sub> (where M is a boron-group element and X is a halogen.)<ref>[[#Henderson|Henderson]], p. 60</ref> [[Fluorine]], the first halogen, is able to form stable compounds with every element that has been tested (except [[neon]] and [[helium]]),<ref>{{cite journal|last1=Young|first1=J. P. |last2=Haire|first2=R. G.|last3=Peterson |first3=J. R. |last4=Ensor |first4=D. D. |last5=Fellow |first5=R. L. |title=Chemical Consequences of Radioactive Decay. 2. Spectrophotometric Study of the Ingrowth of Berkelium-249 and Californium-249 Into Halides of Einsteinium-253 |journal=Inorganic Chemistry |volume=20 |pages=3979–3983 |year=1981 |doi=10.1021/ic50225a076|issue=11}}</ref> and the boron group is no exception. It is even hypothesized that nihonium could form a compound with fluorine, NhF<sub>3</sub>, before spontaneously decaying due to nihonium's radioactivity. [[Chlorine]] also forms stable compounds with all of the elements in the boron group, including thallium, and is hypothesized to react with nihonium. All of the elements will react with [[bromine]] under the right conditions, as with the other halogens but less vigorously than either chlorine or fluorine. [[Iodine]] will react with all natural elements in the periodic table except for the noble gases, and is notable for its explosive reaction with aluminium to form AlI<sub>3</sub>.<ref>{{cite journal|last=Francis |first=William |title=The Chemical Gazette, or Journal of Practical Chemistry |volume=XVI |page=269 |year=1918 |url=https://books.google.com/books?id=-KwRAAAAYAAJ&pg=PA269|location=Boston, Ma}}</ref> [[Astatine]], the fifth halogen, has only formed a few compounds, due to its radioactivity and short half-life, and no reports of a compound with an At–Al, –Ga, –In, –Tl, or –Nh bond have been seen, although scientists think that it should form salts with metals.<ref>{{cite book |title=The Halogen Elements: Fluorine, Chlorine, Bromine, Iodine, Astatine |last=Roza |first=Greg|year=2010 |publisher=The Rozen Publishing Group, Inc. |location=NY, New York, USA |isbn=978-1-4358-3556-6 |page=33 |url=https://books.google.com/books?id=twdXz1jfVOsC}}</ref> [[Tennessine]], the sixth and final member of group 17, may also form compounds with the elements in the boron group; however, because Tennessine is purely synthetic and thus must be created artificially, its chemistry has not been investigated, and any compounds would likely decay nearly instantly after formation due to its extreme radioactivity.<!--At-B bond is known, read astatine. At-F is still controversial, although tried. Uut hypothesis is uncited, literature talks even about UutF5. Also thought iodine doesn't react with sulfur-->

===Physical properties===
It has been noticed that the elements in the boron group have similar [[physical properties]], although most of boron's are exceptional. For example, all of the elements in the boron group, except for boron itself, are [[Hardness|soft]]. Moreover, all of the other elements in group 13 are relatively reactive at moderate [[temperature]]s, while boron's reactivity only becomes comparable at very high temperatures. One characteristic that all do have in common is having three electrons in their [[valence shell]]s. Boron, being a metalloid, is a thermal and electrical insulator at room temperature, but a good conductor of heat and electricity at high temperatures.<ref name="grp.13 elem. chem." /> Unlike boron, the metals in the group are good conductors under normal conditions. This is in accordance with the long-standing [[generalization]] that all metals conduct heat and electricity better than most non-metals.<ref>{{cite book |title=Criminalistics: Forensic Science, Crime and Terrorism |last=Girard |first=James E. |year=2010 |publisher=Jones & Bartlett Learning |page=221 |url=https://books.google.com/books?id=JRe7qd5u0yAC&pg=PA221|isbn=978-0-7637-7731-9}}</ref>

===Oxidation states===
The [[inert pair effect|inert s-pair effect]] is significant in the group-13 elements, especially the heavier ones like thallium. This results in a variety of oxidation states. In the lighter elements, the +3 state is the most stable, but the +1 state becomes more prevalent with increasing atomic number, and is the most stable for thallium.<ref>[[#Henderson|Henderson]], p. 57</ref> Boron is capable of forming compounds with lower oxidization states, of +1 or +2, and aluminium can do the same.<ref>{{cite book |title=Structure and bonding |last= Barrett |first=Jack |year=2001 |publisher=The Royal Society of Chemistry |location=Cambridge, UK |isbn=0-85404-647-X |page=91 |url=https://books.google.com/books?id=-zIM6J1gEJkC}}</ref> Gallium can form compounds with the oxidation states +1, +2 and +3. Indium is like gallium, but its +1 compounds are more stable than those of the lighter elements. The strength of the inert-pair effect is maximal in thallium, which is generally only stable in the oxidation state of +1, although the +3 state is seen in some compounds. Stable and monomeric gallium, indium and thallium radicals with a formal oxidation state of +2 have since been reported.<ref>{{cite journal|last1=Protchenko|first1=Andrey V.|last2=Dange|first2=Deepak|last3=Harmer|first3=Jeffrey R.|last4=Tang|first4=Christina Y.|last5=Schwarz|first5=Andrew D.|last6=Kelly|first6=Michael J.|last7=Phillips|first7=Nicholas|last8=Tirfoin|first8=Remi|last9=Birjkumar|first9=Krishna Hassomal|last10=Jones|first10=Cameron|last11=Kaltsoyannis|first11=Nikolas|last12=Mountford|first12=Philip|last13=Aldridge|first13=Simon|title=Stable GaX<sub>2</sub>, InX<sub>2</sub> and TlX<sub>2</sub> radicals|journal=Nature Chemistry|date=16 February 2014|volume=6|issue=4|pages=315–319|doi=10.1038/nchem.1870|pmid=24651198|bibcode = 2014NatCh...6..315P }}</ref> Nihonium may have +5 oxidation state.<ref name=Haire>{{cite book| title = The Chemistry of the Actinide and Transactinide Elements| editor1-last = Morss|editor2-first = Norman M.| editor2-last = Edelstein| editor3-last = Fuger|editor3-first = Jean| last = Haire|first = Richard G.| chapter = Transactinides and the future elements| publisher = [[Springer Science+Business Media]]| year = 2006| isbn = 1-4020-3555-1| location = Dordrecht, The Netherlands| edition = 3rd}}</ref>

===Periodic trends===
There are several trends that can be observed in the properties of the boron group members. The boiling points of these elements drop from period to period, while densities tend to rise.
[[File:Borgruppe.jpg|thumb|The 5 stable elements of the boron group]]
{| class="wikitable"
!Element !! Boiling point !! Density (g/cm<sup>3</sup>)
|-
| Boron || 4,000&nbsp;°C || 2.46
|-
| Aluminium || 2,519&nbsp;°C || 2.7
|-
| Gallium || 2,204&nbsp;°C || 5.904
|-
| Indium || 2,072&nbsp;°C || 7.31
|-
| Thallium || 1,473&nbsp;°C || 11.85
|}

===Nuclear===
With the exception of the synthetic nihonium, all of the elements of the boron group have stable [[isotopes]]. Because all their [[atomic number]]s are odd, boron, gallium and thallium have only two stable isotopes, while aluminium and indium are [[monoisotopic element|monoisotopic]], having only one, although most indium found in nature is the weakly radioactive <sup>115</sup>In. <sup>10</sup>B and <sup>11</sup>B are both stable, as are <sup>27</sup>Al, <sup>69</sup>Ga and <sup>71</sup>Ga, <sup>113</sup>In, and <sup>203</sup>Tl and <sup>205</sup>Tl.<ref>{{cite book |title= The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities |last1= Aldridge |first1= Simon |first2=Anthony J.|last2=Downs|first3=Tony|last3=Downs |year= 2011 |publisher= John Wiley & Sons |page= ii|url= https://books.google.com/books?id=0AazLrNPoMEC|isbn= 978-0-470-68191-6}}</ref> All of these isotopes are readily found in macroscopic quantities in nature. In theory, though, all isotopes with an [[atomic number]] greater than 66 are supposed to be unstable to [[alpha decay]]. Conversely, all elements with atomic numbers are less than or equal to 66 (except Tc, Pm, Sm and Eu) have at least one isotope that is theoretically energetically stable to all forms of decay (with the exception of [[proton decay]], which has never been observed, and [[spontaneous fission]], which is theoretically possible for elements with atomic numbers greater than 40).

Like all other elements, the elements of the boron group have radioactive isotopes, either found in [[trace radioisotope|trace]] quantities in nature or produced [[Chemical synthesis|synthetically]]. The longest-lived of these unstable isotopes is the [[isotopes of indium|indium isotope]] <sup>115</sup>In, with its extremely long [[half-life]] of {{nowrap|4.41 × 10<sup>14</sup> y}}. This isotope makes up the vast majority of all naturally occurring indium despite its slight radioactivity. The shortest-lived is <sup>7</sup>B, with a half-life of a mere {{nowrap|350±50 × 10<sup>−24</sup> s}}, being the [[isotopes of boron|boron isotope]] with the fewest neutrons and a {{not a typo|half-life long}} enough to measure. Some radioisotopes have important roles in scientific research; a few are used in the production of goods for commercial use or, more rarely, as a component of finished products.<ref>[[#Downs1993|Downs]], pp. 19–24</ref>

==History==
The boron group has had many names over the years. According to former conventions it was Group IIIB in the European naming system and Group IIIA in the American. The group has also gained two collective names, "earth metals" and "triels". The latter name is derived from the Latin prefix ''tri-'' ("three") and refers to the three [[valence electrons]] that all of these elements, without exception, have in their [[valence shell]]s.<ref name="C. Kotz, Treichel, R. Townsend 2009 351"/> The name "triels" was first suggested by International Union of Pure and Applied Chemistry (IUPAC) in 1970.<ref name=Girolami>{{cite journal|last1=Girolami|first1=GS|title=Origin of the Terms Pnictogen and Pnictide|journal=J Chem Educ|date=2009|volume=86|issue=10|pages=1200–1201|doi=10.1021/ed086p1200 |bibcode=2009JChEd..86.1200G }}</ref>

Boron was known to the ancient Egyptians, but only in the mineral [[borax]]. The metalloid element was not known in its pure form until 1808, when [[Humphry Davy]] was able to extract it by the method of [[electrolysis]]. Davy devised an experiment in which he dissolved a boron-containing compound in water and sent an electric current through it, causing the elements of the compound to separate into their pure states. To produce larger quantities he shifted from electrolysis to reduction with sodium. Davy named the element ''boracium''. At the same time two French chemists, [[Joseph Louis Gay-Lussac]] and [[Louis Jacques Thénard]], used iron to reduce boric acid. The boron they produced was [[oxidize]]d to boron oxide.<ref>{{cite book |title=The History and Use of Our Earth's Chemical Elements: A Reference Guide |last=Krebs |first=Robert E. |year=2006 |publisher=Greenwood Press |page= 176 |url=https://books.google.com/books?id=yb9xTj72vNAC&pg=PA182|isbn=978-0-313-33438-2}}</ref><ref name="weeks12">{{Cite journal|doi = 10.1021/ed009p1386|title = The discovery of the elements. XII. Other elements isolated with the aid of potassium and sodium: Beryllium, boron, silicon, and aluminium|year = 1932|last1 = Weeks|first1 = Mary Elvira|author-link1=Mary Elvira Weeks|journal = Journal of Chemical Education|volume = 9|issue = 8|page = 1386|bibcode = 1932JChEd...9.1386W }}</ref>

Aluminium, like boron, was first known in minerals before it was finally extracted from [[alum]], a common mineral in some areas of the world. [[Antoine Lavoisier]] and Humphry Davy had each separately tried to extract it. Although neither succeeded, Davy had given the metal its current name. It was only in 1825 that the Danish scientist [[Hans Christian Ørsted]] successfully prepared a rather impure form of the element. Many improvements followed, a significant advance being made just two years later by [[Friedrich Wöhler]], whose slightly modified procedure still yielded an impure product. The first pure sample of aluminium is credited to [[Henri Etienne Sainte-Claire Deville]], who substituted sodium for potassium in the procedure. At that time aluminium was considered precious, and it was displayed next to such metals as gold and silver.<ref name="weeks12"/><ref>[[#Downs1993|Downs]], p. 15</ref> The method used today, [[electrolysis]] of aluminium oxide dissolved in cryolite, was developed by [[Charles Martin Hall]] and [[Paul Héroult]] in the late 1880s.<ref name="weeks12"/>

[[Image:Sphalerite2USGOV.jpg|thumb|The mineral zinc blende, more commonly known as [[sphalerite]], in which indium can occur.]]

Thallium, the heaviest stable element in the boron group, was discovered by [[William Crookes]] and [[Claude-Auguste Lamy]] in 1861. Unlike gallium and indium, thallium had not been predicted by [[Dmitri Mendeleev]], having been discovered before Mendeleev invented the periodic table. As a result, no one was really looking for it until the 1850s when Crookes and Lamy were examining residues from sulfuric acid production. In the [[spectroscopy|spectra]] they saw a completely new line, a streak of deep green, which Crookes named after the Greek word θαλλός ({{transliteration|grc|thallos}}), referring to a green shoot or twig. Lamy was able to produce larger amounts of the new metal and determined most of its chemical and physical properties.<ref name="Weeks13"/><ref>{{cite book |title=Encyclopedia of the elements: technical data, history, processing, applications |last=Enghag |first=Per |year=2004 |page= 71|publisher=Wiley |url=https://books.google.com/books?id=aff7sEea39EC |isbn=978-3-527-30666-4|bibcode=2004eetd.book.....E }}</ref>

Indium is the fourth element of the boron group but was discovered before the third, gallium, and after the fifth, thallium. In 1863 [[Ferdinand Reich]] and his assistant, [[Hieronymous Theodor Richter]], were looking in a sample of the mineral zinc blende, also known as [[sphalerite]] (ZnS), for the spectroscopic lines of the newly discovered element thallium. Reich heated the ore in a coil of [[platinum]] metal and observed the lines that appeared in a [[spectroscope]]. Instead of the green thallium lines that he expected, he saw a new line of deep indigo-blue. Concluding that it must come from a new element, they named it after the characteristic indigo color it had produced.<ref name="Weeks13">{{cite journal
 | doi = 10.1021/ed009p1413
 | title = The discovery of the elements. XIII. Some spectroscopic discoveries
 | year = 1932
 | last1 = Weeks
 | first1 = Mary Elvira
 |author-link1=Mary Elvira Weeks| journal = Journal of Chemical Education
 | volume = 9
 | issue = 8
 | page = 1413|bibcode = 1932JChEd...9.1413W }}</ref><ref name="Emsley 2006 192">[[#Emsley|Emsley]], p. 192</ref>

Gallium minerals were not known before August 1875, when the element itself was discovered. It was one of the elements that the inventor of the periodic table, [[Dmitri Mendeleev]], had predicted to exist six years earlier. While examining the spectroscopic lines in zinc blende the French chemist [[Paul Emile Lecoq de Boisbaudran]] found indications of a new element in the ore. In just three months he was able to produce a sample, which he purified by dissolving it in a [[potassium hydroxide]] (KOH) solution and sending an electric current through it. The next month he presented his findings to the French Academy of Sciences, naming the new element after the Greek name for Gaul, modern France.<ref>[[#Emsley|Emsley]], pp. 158–159</ref><ref name="Weeks15">{{Cite journal|title = The discovery of the elements. XV. Some elements predicted by Mendeleeff |pages = 1605–1619|last = Weeks|first =  Mary Elvira |author-link=Mary Elvira Weeks|doi=10.1021/ed009p1605|journal = [[Journal of Chemical Education]] |volume =9 |issue =9 |year = 1932|bibcode = 1932JChEd...9.1605W }}</ref>

The last confirmed element in the boron group, nihonium, was not discovered but rather created or synthesized. The element's synthesis was first reported by the Dubna [[Joint Institute for Nuclear Research]] team in Russia and the [[Lawrence Livermore National Laboratory]] in the United States, though it was the Dubna team who successfully conducted the experiment in August 2003. Nihonium was discovered in the [[decay chain]] of [[moscovium]], which produced a few precious atoms of nihonium. The results were published in January of the following year. Since then around 13 atoms have been synthesized and various isotopes characterized. However, their results did not meet the stringent criteria for being counted as a discovery, and it was the later [[RIKEN]] experiments of 2004 aimed at directly synthesizing nihonium that were acknowledged by [[IUPAC]] as the discovery.<ref>{{cite journal|title=Experiments on the synthesis of element 115 in the reaction <sup>243</sup>Am(<sup>48</sup>Ca,xn)<sup>291−x</sup>115| doi=10.1103/PhysRevC.69.021601|year=2004|journal=Physical Review C| volume=69| article-number=021601| last1=Oganessian|first1=Yu. Ts.|last2=Utyonkoy| first2=V.|last3=Lobanov|first3=Yu.|last4=Abdullin|first4=F.|last5=Polyakov|first5=A. |last6=Shirokovsky|first6=I. |last7=Tsyganov|first7=Yu. |last8=Gulbekian|first8=G. |last9=Bogomolov |first9=S.|issue=2|bibcode = 2004PhRvC..69b1601O |url=http://www.jinr.ru/publish/Preprints/2003/178(E7-2003-178).pdf}}</ref>

===Etymology===
The name "boron" comes from the Arabic word for the mineral borax, (بورق, ''boraq'') which was known before boron was ever extracted. The "-on" suffix is thought to have been taken from "carbon".<ref>{{Cite book|title=Word-Building Strategies in Modern English|last=Lavrova|first=Natalie|page=95|year=2010 |isbn=978-3-640-53719-8|location=Germany |publisher=GRIN Verlag |url=https://books.google.com/books?id=Uy0uwU6n84wC&pg=PA95}}</ref> Aluminium was named by Humphry Davy in the early 1800s. It is derived from the Greek word ''alumen'', meaning bitter salt, or the Latin ''[[alum]]'', the mineral.<ref>{{Cite book|title=History and perspectives of language study|author=Bugarski, Ranko|editor=Tomić, Olga Mišeska|editor2=Milorad, Radovanović|page=211|year=2000 |isbn=90-272-3692-5|location=Amsterdam, the Netherlands |publisher=John Benjamins Publishing Co. |url=https://books.google.com/books?id=B9clK7Jb6woC&pg=PA211}}</ref> Gallium is derived from the Latin ''Gallia'', referring to France, the place of its discovery.<ref name="Weeks">{{Cite journal|title = The discovery of the elements. XIII. Some elements predicted by Mendeleeff |pages = 1605–1619|last = Weeks|first =  Mary Elvira |author-link=Mary Elvira Weeks|doi=10.1021/ed009p1605|journal = [[Journal of Chemical Education]] |volume =9 |issue =9 |year = 1932|bibcode = 1932JChEd...9.1605W }}</ref> Indium comes from the Latin word ''indicum'', meaning [[indigo dye]], and refers to the element's prominent indigo spectroscopic line.<ref>{{cite journal|title = Indium|last = Venetskii|first = S.|journal = Metallurgist|volume = 15|issue = 2|pages = 148–150|year = 1971|doi = 10.1007/BF01088126}}</ref> Thallium, like indium, is named after the Greek word for the color of its spectroscopic line: {{transliteration|grc|thallos}}, meaning a green twig or shoot.<ref>{{OEtymD|thallium}}</ref><ref>{{cite journal| doi = 10.1021/ed009p2078| title = The discovery of the elements. XIII. Supplementary note on the discovery of thallium| year = 1932| last1 = Weeks| first1 = Mary Elvira|author-link1=Mary Elvira Weeks| journal = Journal of Chemical Education| volume = 9| issue = 12| page = 2078|bibcode = 1932JChEd...9.2078W }}</ref> "Nihonium" is named after [[Japan]] (''Nihon'' in Japanese), where it was discovered.

==Occurrence and abundance==

===Boron===

Boron, with its atomic number of 5, is a very light element. Almost never found free in nature, it is very low in abundance, composing only 0.001% (10 ppm)<ref name="google979">{{cite book|title = Chemistry and chemical reactivity |author1=Kotz, John C. |author2=Treichel, Paul |author3=Townsend, John Raymond  |name-list-style=amp|publisher = Thomson Books| year = 2009 |location = Belmont, Ca, USA|isbn = 978-0-495-38712-1|volume= 2 | page=979|url=https://books.google.com/books?id=jcn6sgt7RpoC&pg=PA979}}</ref> of the Earth's crust. It is known to occur in over a hundred different minerals and [[ores]], however: the main source is [[borax]], but it is also found in [[colemanite]], [[boracite]], [[kernite]], [[tusionite]], [[berborite]] and [[fluoborite]].<ref>Klein, Cornelis and Hurlbut, Cornelius Jr. (1985) ''Manual of Mineralogy'', Wiley, 20th ed., pp. 343–347, {{ISBN|0-471-80580-7}}</ref> Major world miners and extractors of boron include [[Turkey]], the [[United States]], [[Argentina]], [[China]], [[Bolivia]] and [[Peru]]. Turkey is by far the most prominent of these, accounting for around 70% of all boron extraction in the world. The United States is second, most of its yield coming from the state of [[California]].<ref>{{Cite journal|journal = Mineral Processing and Extractive Metallurgy Review|volume = 9|issue = 1–4|year = 1992|pages = 245–254|doi = 10.1080/08827509208952709|title = Mining and Processing of Borates in Turkey|author1=Zbayolu, G. |author2=Poslu, K. |bibcode = 1992MPEMR...9..245O}}</ref>

===Aluminium===
Aluminium, in contrast to boron, is the most abundant metal in the Earth's crust, and the third most abundant element. It composes about 8.2% (82,000 ppm) of the Earth's crust, surpassed only by [[oxygen]] and [[silicon]].<ref name="google979"/> It is like boron, however, in that it is uncommon in nature as a free element. This is due to aluminium's tendency to attract oxygen atoms, forming several [[aluminium oxide]]s. Aluminium is now known to occur in nearly as many minerals as boron, including [[garnet]]s, [[turquoise]]s and [[beryl]]s, but the main source is the ore [[bauxite]]. The world's leading countries in the extraction of aluminium are [[Ghana]], [[Suriname]], [[Russia]] and [[Indonesia]], followed by [[Australia]], [[Guinea]] and [[Brazil]].<ref>[[#Emsley|Emsley]], pp. 22–26</ref>

===Gallium===
Gallium is a relatively rare element in the Earth's crust and is not found in as many minerals as its lighter homologues. Its abundance on the Earth is a mere 0.0018% (18 ppm).<ref name="google979"/> Its production is very low compared to other elements, but has increased greatly over the years as extraction methods have improved. Gallium can be found as a trace in a variety of ores, including bauxite and [[sphalerite]], and in such minerals as [[diaspore]] and [[germanite]]. Trace amounts have been found in [[coal]] as well.<ref>{{Cite journal|title = Determination of gallium in coal and coal fly ash by electrothermal atomic absorption spectrometry using slurry sampling and nickel chemical modification|author1=Shan Xiao-quan |author2=Wang Wen |author3=Wen Bei |name-list-style=amp|journal = [[Journal of Analytical Atomic Spectrometry]]|year = 1992|volume = 7|page = 761| doi = 10.1039/JA9920700761|issue = 5}}</ref>
The gallium content is greater in a few minerals, including [[gallite]] (CuGaS<sub>2</sub>), but these are too rare to be counted as major sources and make negligible contributions to the world's supply.

===Indium===
Indium is another rare element in the boron group at only 0.000005% (0.05 ppm),.<ref name="google979"/> Very few indium-containing minerals are known, all of them scarce: an example is [[indite]]. Indium is found in several zinc ores, but only in minute quantities; likewise some copper and lead ores contain traces. As is the case for most other elements found in ores and minerals, the indium extraction process has become more efficient in recent years, ultimately leading to larger yields. [[Canada]] is the world's leader in indium reserves, but both the [[United States]] and [[China]] have comparable amounts.<ref>{{cite book|title = Indium: geology, mineralogy, and economics |author = Schwarz-Schampera, Ulrich |author2 = M. Herzig |author3 = Peter |author4 = für Geowissenschaften |author5 = Rohstoffe, Bundesanstalt |name-list-style=amp|publisher = Springer-Verlag| year = 2002|location = Berlin, Germany|isbn = 3-540-43135-7| page=161 |url=https://books.google.com/books?id=k7x_2_KnupMC&pg=PA161}}</ref>

===Thallium===
[[File:Glasfaser Roving.jpg|thumb|right|upright|A small bundle of fiberglass]]
Thallium is of intermediate abundance in the Earth's crust, estimated to be 0.00006% (0.6 ppm).<ref name="google979"/> It is found on the ground in some rocks, in the soil and in clay. Many sulfide ores of [[iron]], [[zinc]] and [[cobalt]] contain thallium. In minerals it is found in moderate quantities: some examples are [[crookesite]] (in which it was first discovered), [[lorandite]], [[routhierite]], [[bukovite]], [[hutchinsonite]] and [[sabatierite]]. There are other minerals that contain small amounts of thallium, but they are very rare and do not serve as primary sources.

===Nihonium===
Nihonium is an element that is never found in nature but has been created in a laboratory. It is therefore classified as a [[synthetic element]] with no stable isotopes.

==Applications==
With the exception of synthetic [[nihonium]], all the elements in the boron group have numerous uses and applications in the production and content of many items.

=== Boron ===
{{Main|Boron#Applications}}
Boron has found many industrial applications in recent decades, and new ones are still being found. A common application is in [[fiberglass]].<ref name="Roesky, Atwood 2003 3–10">{{Cite book|title=Group 13 chemistry III: industrial applications |author=Roesky, H.W.|author2=Atwood, David A. |pages=3–10 |publisher=Springer-Verlag |location=Berlin, Germany |year=2003 |isbn=3-540-44105-0 |url=https://books.google.com/books?id=HLVrEzba4UUC}}</ref> There has been rapid expansion in the market for [[borosilicate glass]]; most notable among its special qualities is a much greater resistance to [[thermal expansion]] than regular glass. Another commercially expanding use of boron and its derivatives is in [[ceramic materials|ceramics]]. Several boron compounds, especially the oxides, have unique and valuable properties that have led to their substitution for other materials that are less useful. Boron may be found in pots, vases, plates, and ceramic pan-handles for its insulating properties.

The compound [[borax]] is used in bleaches, for both clothes and teeth. The hardness of boron and some of its compounds give it a wide array of additional uses. A small part (5%) of the boron produced finds use in agriculture.<ref name="Roesky, Atwood 2003 3–10" />

=== Aluminium ===
{{Main|Aluminium#Applications}}
Aluminium is a metal with numerous familiar uses in everyday life. It is most often encountered in [[construction]] materials, in [[Electricity|electrical]] devices, especially as the [[Electrical conductor|conductor]] in cables, and in tools and vessels for cooking and preserving food. Aluminium's lack of reactivity with food products makes it particularly useful for canning. Its high affinity for oxygen makes it a powerful [[reducing agent]]. Finely powdered pure aluminium oxidizes rapidly in air, generating a huge amount of heat in the process (burning at about {{nowrap|5500 °F}} or {{nowrap|3037 °C}}), leading to applications in [[Thermite welding|welding]] and elsewhere that a large amount of heat is needed. Aluminium is a component of [[alloys]] used for making lightweight bodies for aircraft. Cars also sometimes incorporate aluminium in their framework and body, and there are similar applications in military equipment. Less common uses include components of decorations and some guitars. The element is also sees use in a diverse range of electronics.<ref>{{Cite book|title=the elements of economic geology |last=Gregory |first=J. W. |page=152 |year=2004|publisher=Taylor & Francis|url=https://books.google.com/books?id=I6IOAAAAQAAJ&pg=PA152}}</ref><ref>{{Cite book|title=Uses Of Metals And Metallic Minerals|last=Chatterjee |first=K. K. |page=9|publisher=New Age International |year=2007|url=https://books.google.com/books?id=JfIaFtRqt3cC|isbn=978-81-224-2040-1}}</ref>

=== Gallium ===
{{Main|Gallium#Applications}}
[[Image:Uv-LED.jpg|thumb|right|Gallium is one of the chief components of blue [[LED]]s]]
Gallium and its derivatives have only found applications in recent decades. [[Gallium arsenide]] has been used in [[semiconductors]], in [[amplifiers]], in solar cells (for example in [[satellites]]) and in tunnel [[diode]]s for FM transmitter circuits. Gallium alloys are used mostly for dental purposes. Gallium ammonium chloride is used for the leads in [[transistors]].<ref>{{Cite book|title=Metallurgy for the non-metallurgist |last=Chandler |first=Harry |page=59 |publisher=ASM International |year=1998 |isbn=0-87170-652-0 |url=https://books.google.com/books?id=arupok8PTBEC&pg=PA59 }}</ref> A major application of gallium is in [[LED]] lighting. The pure element has been used as a [[dopant]] in semiconductors,{{citation needed|date=February 2013}} and has additional uses in electronic devices with other elements. Gallium has the property of being able to 'wet' glass and porcelain, and thus can be used to make mirrors and other highly reflective objects. Gallium can be added to alloys of other metals to lower their melting points.

=== Indium ===
{{Main|Indium#Applications}}
Indium's uses can be divided into four categories: the largest part (70%) of the production is used for coatings, usually combined as [[indium tin oxide]] (ITO); a smaller portion (12%) goes into alloys and [[solder]]s; a similar amount is used in electrical components and in semiconductors; and the final 6% goes to minor applications.<ref>{{Cite book|title=Minerals Yearbook: Metals And Minerals; 2005 |author= US Department of the Interior |pages=36–1 |publisher=US Government Printing Office | year=2007 |isbn=978-1-4113-1980-6 |location=Washington, DC |url=https://books.google.com/books?id=1jFYedAYAVAC&pg=SA36-PA1 }}</ref> Among the items in which indium may be found are platings, bearings, display devices, heat reflectors, [[phosphors]], and nuclear [[control rods]]. Indium tin oxide has found a wide range of applications, including glass coatings, [[solar panel]]s, streetlights, electrophoretic displays (EPDs), electroluminescent displays (ELDs), plasma display panels (PDPs), electrochemic displays (ECs), field emission displays (FEDs), [[sodium lamp]]s, windshield glass and [[cathode-ray tube]]s, making it the single most important indium compound.<ref>{{cite book|title = Indium: geology, mineralogy, and economics |last1 = Schwarz-Schampera |last2=M. Herzig |last3=für Geowissenschaften und Rohstoffe|first1 =  Ulrich |first2=Peter |first3=Bundesanstal |publisher = Springer-Verlag| year = 2002|location = Berlin, Germany|isbn = 3-540-43135-7| page=169 |url=https://books.google.com/books?id=k7x_2_KnupMC&pg=PA167}}</ref>

=== Thallium ===
{{Main|Thallium#Applications}}
Thallium is used in its elemental form more often than the other boron-group elements. Uncompounded thallium is used in low-melting glasses, [[photoelectric cells]], switches, mercury alloys for low-range glass thermometers, and thallium salts. It can be found in lamps and electronics, and is also used in [[Myocardial perfusion imaging|myocardial imaging]]. The possibility of using thallium in semiconductors has been researched, and it is a known [[catalyst]] in organic synthesis. [[Thallium(I) hydroxide|Thallium hydroxide]] (TlOH) is used mainly in the production of other thallium compounds. [[Thallium sulfate]] (Tl<sub>2</sub>SO<sub>4</sub>) is an outstanding [[vermin]]-killer, and it is a principal component in some rat and mouse poisons. However, the United States and some European countries have banned the substance because of its high toxicity to humans. In other countries, though, the market for the substance is growing. Tl<sub>2</sub>SO<sub>4</sub> is also used in optical systems.<ref>{{cite book|title =Encyclopaedia of Occupational Health and Safety |last = Mager |first = Jeanne |publisher = International Labor Organization Publications| year = 1998|location = Geneva, Switzerland | page= section 63.40 |url=https://books.google.com/books?id=nDhpLa1rl44C&pg=PT145|isbn =978-92-2-109816-4 }}</ref>

==Biological role==
None of the group-13 elements has a major biological role in complex animals, but some are at least associated with a living being. As in other groups, the lighter elements usually have more biological roles than the heavier. The heaviest ones are toxic, as are the other elements in the same periods. Boron is essential in most plants, whose cells use it for such purposes as strengthening [[cell wall]]s. It is found in humans, certainly as a [[essential trace element]], but there is ongoing debate over its significance in human nutrition. Boron's chemistry does allow it to form complexes with such important molecules as [[carbohydrates]], so it is plausible that it could be of greater use in the human body than previously thought. Boron has also been shown to be able to replace [[iron]] in some of its functions, particularly in the healing of wounds.<ref>{{Cite book|title=The nutritional trace metals |last=Reilly |first=Conor |page=217 |publisher=Blackwell Publishing | year=2004 |isbn=1-4051-1040-6 |location=Ames, Iowa |url=https://books.google.com/books?id=VEcFymWfnYUC&pg=PA217 }}</ref> Aluminium has no known biological role in plants or animals, despite its widespread occurrence in nature.<ref>{{Citation |last=Exley |first=Christopher |title=Aluminum in Biological Systems |date=2013 |encyclopedia=Encyclopedia of Metalloproteins |pages=33–34 |editor-last=Kretsinger |editor-first=Robert H. |place=New York, NY |publisher=Springer |language=en |doi=10.1007/978-1-4614-1533-6_105 |isbn=978-1-4614-1533-6 |editor2-last=Uversky |editor2-first=Vladimir N. |editor3-last=Permyakov |editor3-first=Eugene A.}}</ref> Gallium is not essential for the human body, but its relation to iron(III) allows it to become bound to proteins that transport and store iron.<ref>{{Cite book|title=Biological inorganic chemistry: an introduction |last=Crichton |first=Robert R. |page=9 | year=2008 |isbn=978-0-444-52740-0 |location=UK |url=https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA192}}</ref> Gallium can also stimulate metabolism. Indium and its heavier homologues have no biological role, although indium salts in small doses, like gallium, can stimulate metabolism.<ref name="Emsley 2006 192"/>

==Toxicity==
Each element of the boron group has a unique toxicity profile to plants and animals.

As an example of boron toxicity, it has been observed to harm [[barley]] in concentrations exceeding 20 [[Molar concentration|mM]].<ref>{{cite book |title=Advances in plant and animal boron nutrition |last=Fangsen  |first=Xu |year=2007 |publisher=Springer |page=84 |location=Dordrecht, Netherlands |url=https://books.google.com/books?id=Al8-rzgMqWoC&pg=PA82|isbn=978-1-4020-5382-5}}</ref> The symptoms of boron toxicity are numerous in plants, complicating research: they include reduced cell division, decreased shoot and root growth, decreased production of leaf chlorophyll, inhibition of photosynthesis, lowering of stomata conductance,<ref>{{cite journal |title=Early effects of excess boron on photosynthesis and growth|year=1984 |journal=Journal of Experimental Botany |pages=297–305|doi=10.1093/jxb/35.3.297 |last1=Lovatt |first1=Carol J. |last2=Bates |first2=Loretta M. |volume=35 |issue=3}}</ref> reduced proton extrusion from roots,<ref>{{cite journal |last1=Roldán |first1=Marta |last2=Belver |first2=Andrés |last3=Rodríguez-Rosales |first3=Pilar |last4=Ferrol |first4=Nuria |last5=Donaire |first5=Juan Pedro |title=In vivo and in vitro effects of boron on the plasma membrane proton pump of sunflower roots |journal=Physiologia Plantarum |date=January 1992 |volume=84 |issue=1 |pages=49–54 |doi=10.1111/j.1399-3054.1992.tb08763.x |bibcode=1992PPlan..84...49R }}</ref> and deposition of [[lignin]] and [[suberin]].<ref>{{cite journal |last1=Ghanati |first1=Faezeh |last2=Morita |first2=Akio |last3=Yokota |first3=Hiromi |title=Induction of suberin and increase of lignin content by excess boron in tobacco cells |journal=Soil Science and Plant Nutrition |date=June 2002 |volume=48 |issue=3 |pages=357–364 |doi=10.1080/00380768.2002.10409212|bibcode=2002SSPN...48..357G |s2cid=84906176 }}</ref>

Aluminium does not present a prominent toxicity hazard in small quantities, but very large doses are slightly toxic. Gallium is not considered toxic, although it may have some minor effects. Indium is not toxic and can be handled with nearly the same precautions as gallium, but some of its compounds are slightly to moderately toxic.

Thallium, unlike gallium and indium, is extremely toxic, and has caused many poisoning deaths. Its most noticeable effect, apparent even from tiny doses, is [[hair loss]] all over the body, but it causes a wide range of other symptoms, disrupting and eventually halting the functions of many organs. The nearly colorless, odorless and tasteless nature of thallium compounds has led to their use by murderers. The incidence of thallium poisoning, intentional and accidental, increased when thallium (with its similarly toxic compound, thallium sulfate) was introduced to control rats and other pests. The use of thallium pesticides has therefore been prohibited since 1975 in many countries, including the USA.

Nihonium is a highly unstable element and decays by emitting [[alpha particles]]. Due to its strong [[radioactivity]], it would definitely be extremely toxic, although significant quantities of nihonium (larger than a few atoms) have not yet been assembled.<ref>{{cite book |title=Clinical neurotoxicology: syndromes, substances, environments |last=Dobbs |first=Michael |year=2009 |publisher=Saunders |page=277 |location=Philadelphia |url=https://books.google.com/books?id=Pmcy24y2HyMC&pg=PA277|isbn=978-0-323-05260-3}}</ref>

==Notes==
{{notelist}}

==References==
{{reflist|colwidth=30em}}

===Bibliography===
* {{cite book|ref=Downs1993
|title=Chemistry of aluminium, gallium, indium, and thallium
|last=Downs
|first=Anthony John
|year=1993
|publisher=Chapman and Hall Inc.
|pages= 197–201
|url= https://books.google.com/books?id=v-04Kn758yIC&pg=PA201 |isbn=978-0-7514-0103-5}}
*{{cite book|ref=Emsley
|title=Nature's building blocks: an A-Z guide to the elements
|last=Emsley
|first=John
|year=2006
|publisher=Greenwood Press
|page= 192
|url=https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA192
|isbn=978-0-19-850340-8}}
*{{cite book|ref=Henderson |title=Main group chemistry |author= Henderson, W. |year=2000 |publisher=The Royal Society of Chemistry |location=Cambridge, UK |isbn=0-85404-617-8 |page=6 |url=https://books.google.com/books?id=twdXz1jfVOsC}}

==External links==
*[https://www.britannica.com/EBchecked/topic/436674/oxide oxide (chemical compound) – Britannica Online Encyclopedia]. Britannica.com. Retrieved on 2011-05-16.
*[http://www.rsc.org/chemsoc/visualelements/pages/data/intro_groupiii_data.html Visual Elements: Group 13]. Rsc.org. Retrieved on 2011-05-16.
*[https://web.archive.org/web/20110727214058/http://www.tutorvista.com/content/chemistry/chemistry-iv/p-block-elements/reactivity-elements.php Trends In Chemical Reactivity Of Group 13 Elements]. Tutorvista.com. Retrieved on 2011-05-16.
*[http://www.etymonline.com/index.php?search=Aluminum&searchmode=none] etymonline.com Retrieved on 2011-07-27

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[[Category:Groups (periodic table)]]