Reactivity of group 13 elements

    Boron is inert under normal conditions except for attack by F₂. At high temperatures, it reacts with most non-metals (exceptions include H₂), most metals and with NH₃; the formations of metal borides and boron nitride are of particular importance.

   The reactivities of the heavier group 13 elements contrast with that of the first member of the group. Aluminium readily oxidizes in air (see above); it dissolves in dilute mineral acids but is passivated by concentrated HNO₃. Aluminium reacts with aqueous NaOH or KOH liberating H₂.

   Reactions of Al with halogens at room temperature or with N₂ on heating give the Al(III) halides or nitride. Aluminium is often used to reduce metal oxides, e.g. in the thermite process which is highly exothermic.

   Gallium, indium and thallium dissolve in most acids to give salts of Ga(III), In(III) or Tl(I), but only Ga liberates H₂ from aqueous alkali. All three metals react with halogens at, or just above, 298 K; the products are of the type MX₃ with the exceptions of reactions 12.6 and 12.7.