The electronegativity measures the ability of an atom to draw electrons
to itself in a chemical bond. While it is reported as an atomic property, it
is concerned with bonding within a molecule.
One definition of electronegativity
that was proposed by Mulliken in 1934 is particularly
simple, being a simple arithmetical average:
The larger the electronegativity, the greater the tendency for an atom to draw electrons to itself in a chemical bond.
Elements toward the left of the periodic table have low electron affinities, so they tend to act as electron donors, while atoms to the right of the periodic table have high electronegativities, and they tend to act as electron acceptors.