Electron Affinity

Electron affinity is the energy released by an atom (in the form of gas) when an electron capture to form negative ions. Since the energy is released, given the price of the electron affinity of the minus sign.
The greater the energy released, the negative ions are formed more stable. IIA group elements and VIIIA not form a stable negative ions. Prices positive electron affinity.
In one period, from left to right, electron affinity values tend to increase. In one class, from top to bottom, the electron affinity values tend to decrease.