Which of the following is NOT a semiconductor?

The correct answer is Option (1) → Ag

Semiconductors are elemental, such as Si and Ge, or compound, such as GaAs and CdS. Their energy gap is small but not zero.

Option (1) Ag — Not a semiconductor. Silver is a metal. Its conduction band is partly filled or overlaps the valence band. So it has a large number of free electrons and a very low resistivity.

Option (2) Si — Semiconductor. Silicon is an elemental semiconductor with an energy gap of about 1.1 eV.

Option (3) Ge — Semiconductor. Germanium is an elemental semiconductor with an energy gap of about 0.7 eV.

Option (4) GaAs — Semiconductor. Gallium arsenide is a compound semiconductor.

NCERT (2026-27):
Summary – “4. Semiconductors are elemental (Si, Ge) as well as compound (GaAs, CdS, etc.).”