What is Electron Affinity? What is the trend on the periodic table?

Electron Affinity is the ability of a molecule or atom to gain an electron and become a negative ion.

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch7/ie_ea.html 

 On the periodic table, Electron Affinity decreases from top to bottom and increases from left to right.