Reactivity of the group 2 metals

    Beryllium and magnesium are passivated and are kinetically inert to O₂ and H₂O at ambient temperatures. However, Mg amalgam liberates H₂ from water, since no coating of oxide forms on its surface; Mg metal reacts with steam or hot water.

    Beryllium and magnesium dissolve readily in non-oxidizing acids; magnesium is attacked by nitric acid, whereas beryllium reacts with dilute HNO₃ but is passivated by concentrated nitric acid. Magnesium does not react with aqueous alkali, whereas Be forms an amphoteric hydroxide.

The metals Ca, Sr and Ba exhibit similar chemical behaviours, generally resembling, but being slightly less reactive than, Na. They react with water and acids liberating H₂, and the similarity with Na extends to dissolution in liquid NH₃ to give blue solutions containing solvated electrons. From these solutions, it is possible to isolate hexaammines, [M(NH₃)₆] (M = Ca, Sr, Ba), but these slowly decompose to amides .

  When heated, all the group 2 metals combine with O₂, N₂, sulfur or halogens.

    Differences between the first and later members of group 2 are illustrated by the formation of hydrides and carbides.  When heated with H₂, Ca, Sr and Ba form saline hydrides, MH₂, but Mg reacts only under high pressure. In contrast, BeH₂ is prepared from beryllium alkyls. Beryllium combines with carbon at high temperatures to give Be₂C which possesses an antifluorite lattice. The other group 2 metals form carbides MC₂ which contain the [C≡C]^2-  ion, and adopt NaCl lattices that are elongated along one axis. Whereas Be₂C reacts with water  the carbides of the later metals hydrolyse to yield C₂H₂. CaH₂ is used as a drying agent  but its reaction with water is highly exothermic.

  The carbide Mg₂C₃ (which contains the linear [C₃]^4-  ion isoelectronic with CO₂) is formed by heating MgC₂, or by reaction of Mg dust with pentane vapour at 950 K.  Reaction of Mg₂C₃ with water produces MeC≡CH.