8 Two forms of solid carbon, diamond and graphite, differ in their physical properties due to the differences in their

(1) atomic numbers

(2) crystal structures

(3) isotopic abundances

(4) percent compositions

It would be crystal structure. In graphite, carbon atoms are covalently bonded to form sheets, and these sheets are held together by intermolecular forces (London dispersion, to be exact). In diamond, carbon atoms are each covalently bonded to four neighbors in a covalent network structure.

Two forms of solid carbon, diamond and graphite, differ in their physical properties due to the difference in their Crystal structures.