Ionization Energy

Ionization energy is the energy required by an atom in the form of gas to remove one electron to form positive ions.

The lower the ionization energy, the easier an electron released an atom to form negative ions.
In the periodic table, ionization energy values showed periodicity. In a period from left to right, the ionization energy increased. In one class, from left to right, ionization energy decreased.

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.