In general, the metals of Groups I and II can combine, more or less readily, with many less electropositive elements. The reactivity towards most reagents, for example dry oxygen and dry bromine, increases as the size of the atom increases and the ionisation energy falls. However, when reacting with very small non-metallic elements, for example carbon and nitrogen, the reverse is true, since the very small cation and the very small anion produced in the reaction form a very strong crystal lattice. The lattice energy evolved is sufficiently great to more than compensate for the large ionisation energy of the small atom. Hence, although all Group II elements form nitrides, only lithium amongst the alkali metals is able to do so.
Most of the metals react with water and, therefore, with any aqueous solution giving effectively M+ (Group I) and M2+ (Group II) ions.