Whats an electronegativity?

Electronegativity is the measure of a tendency of an atom to attract the bonding pairs of electrons.

Electronegativity is a measure of how badly an atom wants electrons. The higher an atom's electronegativity, the more greedy it is for electrons, the more it wants to try to steal them from other atom's. This involves a concept called ionic bonding because there are electron givers and electron takers. This has to do with whether an element is a metal or a nonmetal.

Metals are very generous and are willing to let go of or give there electrons away. On the other hand, nonmetals don't give up their electrons.