Question

both diamond and graphite are crystalline covalent solid. in both cases there is no single tiny molecule. Then why there are significant differences in the physical properties of graphite and diamond.​

Answer 1

Both diamond and graphite are made entirely out of carbon, as is the more recently discovered buckminsterfullerene (a discrete soccer-ball-shaped molecule containing carbon 60 atoms). The way the carbon atoms are arranged in space, however, is different for the three materials, making them allotropes of carbon. The differing properties of carbon and diamond arise from their distinct crystal structures.

Answer 2

Answer:

It is mainly due to arrangement of carbon atoms.

Since, in graphite it is arranged in layers, it makes it to cleave easily hence we see that graphite is brittle but diamond is one of the hardest form.