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

Question

Mg: it takes more energy to pull two electrons away from magnesium (Mg) than it does to take from chlorine(Cl).
Mg: magnesium has more valence electrons than chlorine.
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 nearly full.

Answer 1

The best 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 a higher ionization energy than magnesium (Mg) due to its electron configuration. Chlorine has seven valence electrons and is close to having a full outer shell (8 electrons), making it more stable and requiring more energy to remove an electron. In contrast, magnesium has two valence electrons and is further from achieving a full outer shell (8 electrons), so it requires less energy to remove its outer electrons.