JEE Main 2025 Apr 2 Shift 1, Chemistry Q3: Group 17 Elements: The Halogen Family

Examining the first four members of group 17 (F, Cl, Br, I):

Covalent radius: $F<Cl<Br<I$ — increases regularly down the group.

Ionic radius: $F^{-}<C{l}^{-}<B{r}^{-}<I^{-}$ — increases regularly.

First ionization energy: $F>Cl>Br>I$ — decreases regularly.

Electron affinity: The expected smooth trend is broken. Fluorine, despite being the smallest, has a lower electron affinity than chlorine because its tiny 2p shell causes strong electron–electron repulsion on the incoming electron. The observed order is:

$$Cl>F>Br>I$$

$\therefore$ Only electron affinity (B) shows irregularity. Option (3) is correct.