White phosphorus shows chemiluminescence because it:

The correct answer is Option (3) → glows in the dark

Chemiluminescence is the emission of light as a result of a chemical reaction. White phosphorus is very reactive; in moist air it is slowly oxidised, and the energy released in this oxidation is given out as a faint greenish light, so white phosphorus glows in the dark.

Why the other options are incorrect

• Option (1) is poisonous — Incorrect. White phosphorus is poisonous, but toxicity has nothing to do with the emission of light.

• Option (2) is waxy — Incorrect. It is a translucent waxy solid, but this is a physical description, not the reason for the glow.

• Option (4) reacts in inert atmosphere — Incorrect. It dissolves in boiling NaOH in an inert atmosphere to give \( \ce{PH3} \), but this reaction is not the source of the light; the glow comes from slow oxidation by air.

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.

NCERT (Pre-rationalised edition, 2022-23):
Phosphorus – Allotropic Forms – “… White phosphorus is a translucent white waxy solid. It is poisonous, insoluble in water but soluble in carbon disulphide and glows in dark (chemiluminescence).”