Question

What is electron affinity? The electron affinity values of three elements A, B and C of a group are 324, 295 and 333 kJ mol^-1. Arrange these in increasing order of their atomic masses.

Answer 1

Electron affinity (EA) is the energy or enthalpy given off when atom accepts an electron.
Cl_(g) + e^- ----> Cl^-_(g) + (EA)
Along the period electron affinity increases and going down the group electron affinity decreases.
The given electron affinity of three elements A,B,C are 324, 295 and 333 kJ mol^-1. So their order is C>A>B.
Thus the masses are B>A>C. Because the electron affinity decreases along the group and along the group, atomic mass increases.