Editing Gallium (section)

===Halides===
{{See also|Gallium halides}}
Gallium(III) oxide reacts with [[Halogenation|fluorinating agents]] such as [[hydrogen fluoride|HF]] or [[fluorine|{{chem|F|2}}]] to form [[gallium(III) fluoride]], {{chem|GaF|3}}. It is an ionic compound strongly insoluble in water. However, it dissolves in [[hydrofluoric acid]], in which it forms an [[adduct]] with water, {{chem|GaF|3|·3H|2|O}}. Attempting to dehydrate this adduct forms {{chem|GaF|2|OH·''n''H|2|O}}. The adduct reacts with ammonia to form {{chem|GaF|3|·3NH|3}}, which can then be heated to form anhydrous {{chem|GaF|3}}.<ref name="downs" />{{rp|128–129}}

[[Gallium trichloride]] is formed by the reaction of gallium metal with [[chlorine]] gas.<ref name="eagleson" /> Unlike the trifluoride, gallium(III) chloride exists as dimeric molecules, {{chem|Ga|2|Cl|6}}, with a melting point of 78&nbsp;°C. Equivalent compounds are formed with bromine and iodine, [[gallium(III) bromide|{{chem|Ga|2|Br|6}}]] and [[gallium(III) iodide|{{chem|Ga|2|I|6}}]].<ref name="downs" />{{rp|133}}

Like the other group 13 trihalides, gallium(III) halides are [[Lewis acid]]s, reacting as halide acceptors with alkali metal halides to form salts containing {{chem|GaX|4|-}} anions, where X is a halogen. They also react with [[haloalkane|alkyl halides]] to form [[carbocation]]s and {{chem|GaX|4|-}}.<ref name="downs" />{{rp|136–137}}

When heated to a high temperature, gallium(III) halides react with elemental gallium to form the respective gallium(I) halides. For example, {{chem|GaCl|3}} reacts with Ga to form {{chem|GaCl}}:
:2 Ga + {{chem|GaCl|3}} {{eqm}} 3 GaCl (g)

At lower temperatures, the equilibrium shifts toward the left and GaCl disproportionates back to elemental gallium and {{chem|GaCl|3}}. GaCl can also be produced by reacting Ga with HCl at 950&nbsp;°C; the product can be condensed as a red solid.<ref name="wiberg_holleman" />{{rp|1036}}

Gallium(I) compounds can be stabilized by forming adducts with Lewis acids. For example:
:GaCl + {{chem|AlCl|3}} → {{chem|Ga|+|[AlCl|4|]|-}}

The so-called "gallium(II) halides", {{chem|GaX|2}}, are actually adducts of gallium(I) halides with the respective gallium(III) halides, having the structure {{chem|Ga|+|[GaX|4|]|-}}. For example:<ref name="eagleson" /><ref name="wiberg_holleman" />{{rp|1036}}<ref name="arora">{{cite book
|title= Text Book Of Inorganic Chemistry
|author= Arora, Amit
|publisher= Discovery Publishing House
|date= 2005
|isbn= 978-81-8356-013-9
|pages= 389–399
}}</ref>
:GaCl + {{chem|GaCl|3}} → {{chem|Ga|+|[GaCl|4|]|-}}