Question

For electron affinity of halogens which of the following is/are correct ?

• A. $Br>F$
• B. $Cl>F$
• C. $Br>Cl$
• D. $F>I$

Answer 1

Answer: (B), (D)

$F>I$

Electron affinity decreases in a group from top to bottom due to increase in size so the expected order of electron affinity for halogens is $F>Cl>Br>I$
However , It is not so. The electron affinity of elements of III period is higher than that of II period because elements of II period have a small size and greater electron density so the incomming electrons suffer a repulsive force Thus the order of electron affinity is $Cl>F>Br>I$
Hence options (b),(d) are the correct options.