The "opposite" of ionization energy is

A. atomic energy.

B. electronegativity.

C. molecular energy.

D. electromagnetic energy.

The opposite of ionization energy is B, electronegativity. In short, we can define ionization energy as the amount of energy required to remove one electron from the outermost valence shell from an atom. Conversely, we can define electronegativity as an atom's "willingness" to accept one electron.