1. Tardigrade
  2. Question
  3. Chemistry
  4. For electron affinity of halogens which of the following is correct ?

Q. For electron affinity of halogens which of the following is correct ?

 2279  242 AIIMSAIIMS 2004Classification of Elements and Periodicity in Properties Report Error

Solution:

Electron affinity is defined as the amount of energy released when an electron is added to the outermost shell of gaseous, neutral isolated atom. Electron affinity decrease in a group from top to bottom due to increase in size, so the expected order of EA for halogens is

But it is not so. It is observed that of elements of III period > II period, this is because elements of second period have small size and greater electron density so, the incoming electrons suffer a repulsive force.
Thus, the order of EA is