Question

Which of the following are covalent solids?

• A. Iron
• B. Diamond
• C. Sodium chloride
  
• D. Graphite

Answer 1

Answer: (B), (D)

The correct options are
B Diamond
D Graphite

Covalent solids form crystals that can be viewed as a single giant molecule made up of an almost endless number of covalent bonds.

Each carbon atom in diamond and graphite is covalently bound to four other carbon atoms oriented toward the corners of a tetrahedron. Because all of the bonds in this structure are equally strong, covalent solids are often very hard and they are notoriously difficult to melt. Diamond is the hardest natural substance and it melts at ${355}^{o}C$.

Hence, the correct options are $B$ and $D$