Question

Which of the following statements are true regarding allotropes of carbon?

• A. Graphite is extremely harder than diamond.
• B. Graphite has higher electrical conductivity than diamond.
• C. Graphite has higher thermal conductivity than diamond.
• D. Graphite has lower density than diamond.

Answer 1

Answer: (B), (D)

The correct options are
B Graphite has higher electrical conductivity than diamond.
D Graphite has lower density than diamond.

$\bullet$ Diamond has a 3-D network of strong covalent bonds, which makes it extremely hard. In diamond, all four valence electrons of each carbon atom are covalent bonded and has no free electrons conduct electricity. Hence, diamond is a poor conductor of electricity.

$\bullet$ In graphite, each carbon atoms utilizes only three valence electrons for forming covalent bonds, the fourth valence electron is mobile, and is responsible for conducting electricity.

$\bullet$ The layers in graphite are held by weak van der Waals forces making graphite soft and slippery. Therefore, density of graphite is lower than diamond.