Contrast the following terms and give one exapmle for each, Electronegativity and electro affinity?

#"Electronegativity"# is conceived to be the ability of an atom involved in a chemical bond to polarize electron density towards itself. There are various scales, of which the Pauling Scale was the earliest and is still widely used.

On the other hand, #"electron affinity"# is approached by a direct measurement...i.e. the enthalpy associated with the formation of ONE MOLE of gaseous ANION, from one mole of gaseous atoms, and ONE mole of electrons...

#X(g) + e^(-) rarr X^(-)(g) + Delta#

#Delta# might of course be positive or negative... In general electron affinity INCREASES across the Period from left to right as we face the Table....

Electronegativity is a measure of how strongly an atom pulls a pair of bonding electrons towards itself. So fluorine, with an electronegativity of 4.0, is able to pull bonding electrons the most towards it when bonded to another element. Whereas an element like iodine weakly pulls bonding electrons towards itself.

Electron affinity is a measure of the energy released or put into to make a gaseous atom gain an electron:
First E.A: #X_((g))+e^-##-> X^-##""_((g))#

Even though fluorine has the highest electronegativity, chlorine has the highest electron affinity, it releases 349kJ of energy per mole of chlorine atoms in the reaction:
#Cl_((g))+e^(-)-> Cl^(-)""_((g)),# #DeltaH=-349"kJ mol"^-1#