Electron Affinity - It the amount of energy released when an electron is added in the outermost shell of gaseous atom.
Unit - KJ/ Mole
Affinity means attraction - that is why neutral atom attracts the electron towards it self
Electron Affinity increases in Period:
In a period electron affinity increases from left to right due to decrease of atomic size because when size of atom decreases the attraction between nucleus and incoming electron increases
Electron Affinity decreases in Groups :
It decreases from top to bottom because size of an atom increases along the shell number so attraction between nucleus and outermost electron decreases as the result low energy releases. so greater the size - lower the electron affinity
