If we look at some of the compounds of these elements we find
similar behaviour. Thus the hydrides of Group ynB elements
(excepting hydrogen fluoride, p. 52) show an increase in melting
and boiling points as we go down the group. These are generally
low, in contrast to the melting and boiling points of the Group IA
metal chlorides (except lithium chloride) which are high and decrease
down the group. The values are shown in Figure 1.9(a) and (b).