Question

for element x represented above, which of the following is the most likely explanation for the large difference between the second and third ionization energies?
a the effective nuclear charge decreases with successive ionizations.
b the shielding of outer electrons increases with successive ionizations.
c the electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.
d the ionic radius increases with successive ionizations.

Explanation:

• Option A: Effective nuclear charge increases with successive ionizations as electrons are removed, so this option is incorrect.
• Option B: Shielding of outer electrons decreases with successive ionizations (fewer electrons to shield), so this option is incorrect.
• Option C: When removing the third electron, if the first two electrons were from the outer - shell (valence electrons), and the third electron is from an inner - shell (core electron). Core electrons are much closer to the nucleus. The large jump in ionization energy (\(IE_3\) is much larger than \(IE_2\)) is because the electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.
• Option D: Ionic radius decreases with successive ionizations (more positive charge, electrons are pulled in more), so this option is incorrect.

Answer:

C. The electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.