Solve 7th one and give proper explanation
Q.7. The hardest compound of boron is:
(a) boric acid
(b) boron nitride
(c) boron carbide
(d) boron hydride
Boron carbide has a complex crystal structure typical of icosahedron-based borides. There, B12 icosahedra form a rhombohedral lattice unit surrounding a C-B-C chain that resides at the center of the unit cell, and both carbon atoms bridge the neighbouring three icosahedra.
Due to this highly complex and strong structure it is hardest compound after cubic boron nitride and diamond.
The correct option is (c). Boron Carbide.