Which of the following is a covalent solid ?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(SiC\)
Crystalline solids are classed by the forces that hold their particles together. In covalent or network solids the atoms are joined by covalent bonds throughout the crystal. In silicon carbide every Si atom is bonded tetrahedrally to four C atoms and every C to four Si atoms, so SiC is a covalent solid.
Why the other options are incorrect
Option (1) ZnS — Incorrect. An ionic solid, made of \( \ce{Zn^{2+}} \) and \( \ce{S^{2-}} \) ions held by electrostatic forces.
Option (2) Ag — Incorrect. A metallic solid; positive ions are held in a sea of mobile electrons, which makes it a good conductor.
Option (4) CCl4 — Incorrect. A non-polar molecular solid; separate \( \ce{CCl4} \) molecules are held by weak dispersion (London) forces, so it melts at a low temperature.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Different Types of Solids (row of Table 1.2)
| Type of Solid | Constituent Particles | Bonding/Attractive Forces | Examples | Physical Nature | Electrical Conductivity | Melting Point |
|---|---|---|---|---|---|---|
| (4) Covalent or network solids | Atoms | Covalent bonding | SiO2 (quartz), SiC, C (diamond), AlN, C (graphite) | Hard | Insulators (graphite: conductor, exception) | Very high |