Which of the following is not a paramagnetic substance?

The correct answer is Option (4) → Alnico

A paramagnetic substance gets weakly magnetised in an external magnetic field, while a ferromagnetic substance gets strongly magnetised.

Option (1) Calcium — Paramagnetic. Calcium is weakly magnetised in an external field and is weakly attracted to a magnet.

Option (2) Sodium — Paramagnetic. Sodium, like calcium, is weakly magnetised and weakly attracted to a magnet.

Option (3) Copper chloride — Paramagnetic. This compound is also only weakly magnetised in an external field.

Option (4) Alnico — Not paramagnetic. Alnico is an alloy of iron, aluminium, nickel, cobalt and copper. It is a hard ferromagnet. It is strongly magnetised and keeps its magnetisation after the field is removed. So it is used to make permanent magnets.

NCERT (2026-27):
Paramagnetism – “Some paramagnetic materials are aluminium, sodium, calcium, oxygen (at STP) and copper chloride.”

Ferromagnetism – “… In some ferromagnetic materials the magnetisation persists. Such materials are called hard magnetic materials or hard ferromagnets. Alnico, an alloy of iron, aluminium, nickel, cobalt and copper, is one such material.”