What is the difference between Ionization energy and Electron Affinity?

Question

rogue · Answer

Ionization energy is the energy it takes to remove the outermost electron from a neutral atom in the gas phase. Electron affinity is the energy given off when a neutral atom in the gas phase gains an extra electron. Electron affinity is much harder to measure than ionization energy. Generally, both electron affinity and ionization energy increase as you go up the periodic table, and as you go to the right of the table.

anonymous · Answer

The ionization energy of a chemical species, i.e. an atom or molecule, is the energy required to remove electrons from gaseous atoms or ions.

The Electron affinity of an atom or molecule is defined as the amount of energy released when an electron is added to a neutral atom or molecule to form a negative ion.

The difference is 
Ionization energy is related with making cations from neutral atoms and electron affinity is related with making anions.