CBSE Class 10 Answered

Differences between diamond and graphite:
(a) Diamond is denser than graphite. The density of diamond is 3.514g cm^-3 while that of graphite is 2.226 g cm-^3.

(b) Diamond is hard while graphite is soft. Graphite has lubricating properties.

(c)Diamond is a bad conductor of electricity while graphite is a good conductor of electricity.

(d)Diamond is extremely chemically unreactive whereas graphite is quite reactive.

In diamond each carbon atom is surrounded by four other carbon atoms bonded by four covalent bonds. While in graphite, each carbon atom is surrounded by three other carbon atoms. One of the three bonds is double bond. Therefore, out of the four valence electrons in a carbon atom, only three are used for bonding and the fourth is relatively free and can move from one carbon atom to the other. These free electrons can carry electricity and make graphite a good conductor of electricity.