The effective nuclear charge experienced by the outermost electron of Na is different than the effective nuclear charge experienced by the outermost electron of Ne. This difference best accounts for which of the following

B. Na has a lower first ionization energy than Ne.

Explanation:

Ionization energy is the energy needed to move an electron from a molecule or gaseous molecule.The factors that affect the ionization energy are:

The size of the positively charged nuclear-the more positively charged the molecule is the more energy needed to remove an electron.Size of the atom- an increase in the molecule/atom size, the less ionization energy needed to remove an electron, because with an increase in size the attraction between the positive nucleus and the electron decreases.Shielding effects of the inner shell electron-increase in shielding results in the decrease of the ionization energy.

Ne atom is bigger than the Na atom.