FORMATION OF IONS
We note first that the elements are all electropositive, having relatively low ionisation energies, and are, in consequence, very reactive. The enthalpy change required for the process M(metal) -» M + (g) for Group I, or M(metal) -> M2+(g) for Group II is at a maximum at the top of each group, and it is, therefore, not surprising to find that lithium, beryllium and, to some extent, magnesium do form some covalent compounds. Most solid compounds of Group 1 and II elements, however, have ionic structures and the properties associated with such structures—high m.p. and b.p., solubility in water rather than in organic solvents and electrical conductance when molten.