Which has a higher ionization energy: chlorine (CI) or magnesium (Mg)? Why?

Question

Select the best answer. (1 point)
© Cl; it takes less energy to add an electron to a valence shell that is nearly full.
Cl, it takes much more energy to pull an electron away from a valence shell that is neary full.
• Mg; magnesium has more valence electrons than chlorine.
Mg; it takes more energy to pull two electrons away from magnesium (Mg) than it does to take them from chlorine(Cl).

Answer 1

The correct answer is: Cl; it takes much more energy to pull an electron away from a valence shell that is nearly full.

This is because chlorine (Cl) has an electron configuration that is closer to achieving a stable noble gas configuration, as it has 7 valence electrons and needs only one more to achieve stability. Consequently, removing an electron from chlorine requires significantly more energy due to its high effective nuclear charge and nearly full valence shell. In contrast, magnesium (Mg), with 2 valence electrons, is less stable and thus has a lower ionization energy.