Electron affinity is the energy gained by an atom when it attracts an electron.
The electron affinity of an atom is the amount of energy gained by that atom when it attracts an electron. The more negative the value, the more strongly that atom will attract electrons to itself. Electron affinity is measured in kilojoules per mole (kJ/mol). The higher this value, the stronger that element’s attraction to electrons. For example, oxygen has a negative electron affinity of -0.898 kJ/mol and fluorine has a negative electron affinity of -2.8 kJ/mol.
