Give reasons for the following:
a. Alkali metals are soft and volatile.
b. First ionisation enthalpies of alkali metals are low.

Explanation

a. Alkali metals have only one valence electron per metal atom. The binding energies in the closed packed metal lattice are weak. That is why alkali metals are soft and volatile.
b. Alkali metals have larger and the valence shell electron `(ns^(1))` is loosely bond and can be removed easily by providing low amount of energy. That is why the first ionisation enthalpies of all alkali metals are low. `M_((g))overset(IE_(1))rarr M_((g))^(o+)+ bar e`