An n-type semiconductor has a large number of free electrons. Yet it…

The correct answer is Option (3) → The total number of protons equals the total number of electrons.

Option (1) It has an equal number of holes. — Incorrect. In an n-type semiconductor, electrons are the majority carriers and holes are the minority carriers (\( n_e\gg n_h \)). So the holes are far fewer than the free electrons.

Option (2) It has no free electrons. — Incorrect. Each pentavalent donor atom gives one free electron, so the electrons become the majority carriers.

Option (3) The total number of protons equals the total number of electrons. — Correct. Silicon and the donor atoms are neutral to begin with. A donor that gives up its fifth electron is left as a positively charged ionised core. So the charge of each extra free electron is just balanced by its core. The crystal as a whole stays neutral.

Option (4) It is not electrically neutral. — Incorrect. Doping adds neutral atoms. No charge is brought in from outside, so the crystal as a whole carries no net charge.

NCERT (2026-27):
Extrinsic Semiconductor – “Note that the crystal maintains an overall charge neutrality as the charge of additional charge carriers is just equal and opposite to that of the ionised cores in the lattice.”