Which has a higher ionization energy: chlorine (Cl) or magnesium (Mg)? Why? Select the best answer.

Question

A. Cl; it takes much more energy to pull an electron away from a valence shell that is nearly full.
B. Mg; it takes more energy to pull two electrons away from magnesium(Mg) than it does to take them from chlorine(Cl).
C. Cl; it takes less energy to add an electron to a valence shell that is nearly full.
D. Mg; magnesium has more valence electrons than chlorine.

Answer 1

The best answer is:

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

Explanation: Chlorine has a higher ionization energy than magnesium because chlorine is a non-metal with a nearly full valence shell (7 out of 8 electrons), and it takes more energy to remove an electron from this stable configuration. In contrast, magnesium has 2 valence electrons and is more willing to lose them, resulting in a lower ionization energy. Thus, option A correctly explains the reasoning behind chlorine's higher ionization energy compared to magnesium.