Editing Gallium (section)

===Oxides and chalcogenides===
Gallium reacts with the [[chalcogen]]s only at relatively high temperatures. At room temperature, gallium metal is not reactive with air and water because it forms a [[passivation (chemistry)|passive]], protective [[oxide]] layer. At higher temperatures, however, it reacts with atmospheric [[oxygen]] to form [[gallium(III) oxide]], {{chem|Ga|2|O|3}}.<ref name="eagleson">{{cite book
|title= Concise encyclopedia chemistry
|url= https://archive.org/details/conciseencyclope00eagl
|url-access= registration
|editor= Eagleson, Mary
|publisher= Walter de Gruyter
|date= 1994
|isbn= 978-3-11-011451-5
|page= [https://archive.org/details/conciseencyclope00eagl/page/438 438]
}}</ref> Reducing {{chem|Ga|2|O|3}} with elemental gallium in vacuum at 500&nbsp;°C to 700&nbsp;°C yields the dark brown [[gallium(I) oxide]], {{chem|Ga|2|O}}.<ref name="downs" />{{rp|285}} {{chem|Ga|2|O}} is a very strong [[reducing agent]], capable of reducing [[sulfuric acid|{{chem|H|2|SO|4}}]] to [[hydrogen sulfide|{{chem|H|2|S}}]].<ref name="downs" />{{rp|207}} It disproportionates at 800&nbsp;°C back to gallium and {{chem|Ga|2|O|3}}.<ref name="emeleus_sharpe">{{cite book |title= Advances in inorganic chemistry and radiochemistry |volume= 5 |author= Greenwood, N. N. |editor= Harry Julius Emeléus |editor-link= Harry Julius Emeléus |editor2= Alan G. Sharpe |publisher= Academic Press |date= 1962
|isbn= 978-0-12-023605-3 |pages= 94–95}}</ref>

[[Gallium(III) sulfide]], {{chem|Ga|2|S|3}}, has 3 possible crystal modifications.<ref name="emeleus_sharpe" />{{rp|104}} It can be made by the reaction of gallium with [[hydrogen sulfide]] ({{chem|H|2|S}}) at 950&nbsp;°C.<ref name="downs" />{{rp|162}} Alternatively, {{chem|Ga(OH)|3}} can be used at 747&nbsp;°C:<ref>{{cite book |title= Semiconductors: data handbook |author= Madelung, Otfried |edition= 3rd |publisher= Birkhäuser |date= 2004 |isbn= 978-3-540-40488-0 |pages= 276–277}}</ref>
:2 {{chem|Ga(OH)|3}} + 3 {{chem|H|2|S}} → {{chem|Ga|2|S|3}} + 6 {{chem|H|2|O}}

Reacting a mixture of alkali metal carbonates and {{chem|Ga|2|O|3}} with {{chem|H|2|S}} leads to the formation of ''thiogallates'' containing the {{chem|[Ga|2|S|4|]|2-}} anion. Strong acids decompose these salts, releasing {{chem|H|2|S}} in the process.<ref name="emeleus_sharpe" />{{rp|104–105}} The mercury salt, {{chem|HgGa|2|S|4}}, can be used as a [[phosphor]].<ref>{{cite journal |author= Krausbauer, L. |author2= Nitsche, R. |author3= Wild, P. |year= 1965 |title= Mercury gallium sulfide, {{chem|HgGa|2|S|4}}, a new phosphor |journal= Physica |volume= 31 |issue= 1 |pages= 113–121 |doi= 10.1016/0031-8914(65)90110-2|bibcode= 1965Phy....31..113K}}</ref>

Gallium also forms sulfides in lower oxidation states, such as [[gallium(II) sulfide]] and the green [[gallium(I) sulfide]], the latter of which is produced from the former by heating to 1000&nbsp;°C under a stream of nitrogen.<ref name="emeleus_sharpe" />{{rp|94}}

The other binary chalcogenides, {{chem|Ga|2|Se|3}} and {{chem|Ga|2|Te|3}}, have the [[zincblende (crystal structure)|zincblende]] structure. They are all semiconductors but are easily [[hydrolysis|hydrolysed]] and have limited utility.<ref name="emeleus_sharpe" />{{rp|104}}