Which one of the following element is a semi conductor?

The correct answer is B) Silicon. Silicon is a metalloid from Group 14 and the standard semiconductor element. Its conductivity lies between that of metals and insulators, because it has a small band gap (about 1.1 eV at room temperature). Electrons can be pushed across that gap by heat, light or doping, which is why conductivity can be controlled.

The other options are all metals and therefore good conductors:

• A) Aluminium is a conductor with no band gap, widely used in power cables.
• C) Silver has the highest electrical conductivity of all metals.
• D) Lead is a conductive metal, used in batteries and solders.

The core concept is band theory: conductors overlap their valence and conduction bands, insulators have a large gap, and semiconductors have a small, tunable gap. For Mains, this links to the semiconductor and electronics sector, including India Semiconductor Mission (2021) and the fab-building push, which rests on silicon wafers.

Trap: Aspirants sometimes pick a metal because silicon looks shiny, or confuse semiconductors with metalloids in general. Germanium is also a semiconductor, but it was not an option here.