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

Question

1. Mg; magnesium has more valence electrons than chlorine.

2.Mg; it takes more energy to pull two electrons away from magnesium(Mg) than it does to take them from chlorine(Cl).

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

4.Cl; it takes less energy to add an electron to a valence shell that is nearly full.

Answer 1

The correct answer is:

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

Explanation:

Chlorine (Cl) has an electron configuration of [Ne] 3s² 3p⁵, meaning it has seven valence electrons and is very close to having a full octet. Removing an electron from a nearly full outer shell requires significantly more energy because atoms generally prefer to maintain their stable electron configurations.

In contrast, magnesium (Mg) has an electron configuration of [Ne] 3s², which means it has two valence electrons. While removing these electrons does require energy, it's generally less than the energy required to remove an electron from a nearly full shell like that of chlorine. Hence, chlorine has a higher ionization energy than magnesium.