The Trend of Electron Affinity in Periodic Table

    The electron affinity (E_ea) of a molecule or an atom or is the amount of energy spent or released when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.

Factors affecting the electron affinity:-

1) Atomic size:- Atomic size increases ELECTRON AFFINITY decreases.

2)Nuclear Charge:- Nuclear Charge ELECTRON AFFINITY increases.

TREND OF The electron affinity  IN PERIODIC TABLE:-

In the period:- In the period from left to right  electron affinity increases because

1) Nuclear Charge increases from left to right in the period.

2)Atomic size decreases

3)Hence In the period from left to right electrons can be easily added thus more elections gets combined means more energy liberates.

In the group: -from top to the bottom electron affinity of elements decreases because-

1)atomic size goes on increases from top to bottom in the same group.

2)Hence attraction force between the nucleus and valence electron decreases.

3) Thus a lesser chance of electrons getting added means minor energy liberation.