Match List I with List II
| List I | List II |
| A. Mg in solid state | I. p-type Semiconductor |
| B. \(MgCl_2\) in molten state | II. n-type Semiconductor |
| C. Silicon with phosphorus | III. Electrolytic conductor |
| D. Germanium with boron | IV. Electronic conductor |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-IV, B-III, C-II, D-I
A current is carried by moving charges. In a metal these are electrons (electronic conduction); in a molten or dissolved ionic compound they are ions (electrolytic conduction). Doping silicon or germanium with an impurity of another group makes a semiconductor.
(A) Mg in solid state — This matches (IV) Electronic conductor. Magnesium is a metal; its current is carried by the movement of electrons, which is metallic or electronic conductance.
(B) MgCl2 in molten state — This matches (III) Electrolytic conductor. In the melt the \( \ce{Mg^2+} \) and \( \ce{Cl^-} \) ions are free to move, and the ions carry the current.
(C) Silicon with phosphorus — This matches (II) n-type Semiconductor. Si (group 14) has four valence electrons and P (group 15) has five. Four of P’s electrons form bonds with four Si atoms; the fifth is free and carries the current, so the carriers are negative (n-type).
(D) Germanium with boron — This matches (I) p-type Semiconductor. B (group 13) has only three valence electrons, so one of the four bonds with Ge lacks an electron. This electron hole moves through the crystal like a positive charge (p-type).
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.