Question

How are electron affinity and ionization energy related?

Answer 1

One is the energy required to remove an electron from an atom. The other is the energy involved when an electron adds to an atom.

Ionization energy I is the amount of energy required to remove the outermost electron an atom. For example,

Ca → Ca⁺ + e⁻; I = 589.8 kJ/mol

Electron affinity EA is the amount of energy involved when an electron adds to an atom. For example,

Ca + e⁻ →Ca⁻; EA = 2.37 kJ/mol

In the Periodic Table, both the ionization energy and the electron affinity of an atom decrease as you go down a Group. They increase as you go across a period. But there are some exceptions to these patterns.