Relationships between the molar volumes of mixtures of elements and their compounds

The molar volumes of stoichiometric mixtures of Group I–III metals and Group V–VII nonmetals are compared with the molar volumes of MX compounds. The derivatives of the B-subgroup metals have the molar volumes larger than the mixtures. The compounds of A-subgroup metals have smaller volumes than the mixtures. A crystal-chemical interpretation of this fact is advanced.