The correct option is Graphite.
Explanation
Carbon exhibits allotropy, meaning it exists in multiple physical forms with different structural arrangements. While non-metals are typically poor conductors of electricity due to the absence of free electrons, specific structural characteristics in certain allotropes can lead to exceptions.
Detailed Analysis:
- Graphite (Correct): In graphite, each carbon atom is bonded to three other carbon atoms in the same plane, forming hexagonal arrays. The fourth valence electron of each carbon atom remains unbonded and becomes delocalized. These free electrons can move freely between the layers, making graphite a good conductor of electricity.
- Diamond: In diamond, each carbon atom is covalently bonded to four other carbon atoms in a rigid tetrahedral structure. All four valence electrons are involved in bonding, leaving no free electrons to conduct electricity. Therefore, diamond is an electrical insulator.
- Fullerene: Fullerenes (e.g., C60) consist of carbon atoms arranged in hollow cages (spheres, ellipsoids, or tubes). While they possess delocalized electrons within the molecule, pure solid fullerene is generally a semiconductor or insulator, not a good conductor like graphite.
- Sulphur: Sulphur is a non-metal that exists as polyatomic molecules (S8). It lacks free electrons and is a poor conductor of electricity.
Key Takeaway:
Graphite is a good conductor of electricity because of its layered structure and the presence of free, delocalized π-electrons, unlike diamond where all electrons are localized in bonds.