Which of the following is the most reactive compound?

The correct answer is Option (4) → \(F_2\)

Fluorine is the most reactive of all the halogens. Its F–F bond is weak (small atoms, strong repulsion between the lone pairs) and fluorine is the most electronegative element, so \( \ce{F2} \) is the strongest oxidising agent.

Interhalogen compounds are in general more reactive than halogens, except fluorine, because the X–X′ bond in an interhalogen is weaker than the X–X bond of a halogen (the F–F bond is the exception). So the reactivity runs

    \( \ce{F2} \) > ICl > \( \ce{Cl2} \), \( \ce{I2} \)

and the most reactive substance here is F₂.

Why the other options are incorrect

• Option (1) \(ICl\) — Incorrect. As an interhalogen it is more reactive than \( \ce{Cl2} \) and \( \ce{I2} \) (the I–Cl bond is weaker and polar), but it is less reactive than fluorine.

• Option (2) \(Cl_2\) — Incorrect. The Cl–Cl bond is the strongest of the halogens, and chlorine is less electronegative than fluorine.

• Option (3) \(I_2\) — Incorrect. Iodine is the weakest oxidising agent of the halogens given and the least reactive.

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):
Properties – “… In general, interhalogen compounds are more reactive than halogens (except fluorine). This is because X–X′ bond in interhalogens is weaker than X–X bond in halogens except F–F bond.”