In Chapter 2, a discussion of the theory of metallic bonding
indicated that the strength of such bonding generally depends on
the ratio (number of electrons available for bonding)/(atomic size).
The greater this ratio is, the stronger are the bonds between the
metal atoms. In the pre-transition metals, this ratio is small and at a
minimum in Group I with only one bonding electron. Metallic
bond strength is greater in Group II but there are still only two
bonding electrons available, hence the metals are still relatively soft
and have low melting and boiling points. Hardness, m.p. and b.p.
all decrease steadily down Group I, the metallic bond strength
decreasing with increasing atomic radius. These changes are not so