Arrange the following in increasing order of their conductivity (A) S…

The correct answer is Option (1) → (D), (A), (B), (C)

Electrical conductivity depends on the availability of free charge carriers:

• Insulators $\rightarrow$ almost no free electrons
• Semiconductors $\rightarrow$ limited charge carriers
• Metals $\rightarrow$ large number of free electrons

(D) Glass

Glass is an insulator. It has tightly bound electrons and practically no free charge carriers at room temperature. Hence, it has the lowest conductivity.

(A) Silicon

Silicon is a semiconductor. It conducts slightly due to thermally generated charge carriers. Conductivity is low but higher than glass.

(B) Germanium

Also a semiconductor, but its band gap is smaller than silicon, so more charge carriers are available. Therefore, conductivity of germanium $>$ silicon.

(C) Sodium

Sodium is a metal with free electrons in the conduction band. Metals have very high conductivity, so sodium is the highest.

Hence, answer is OPTION 1 - (D), (A), (B), (C)