Question

Which has a higher ionization energy: chlorine (Cl) or magnesium (Mg)? Why? Select the best answer.(1 point)%0D%0AResponses%0D%0A%0D%0AMg; magnesium has more valence electrons than chlorine.%0D%0AMg; magnesium has more valence electrons than chlorine.%0D%0A%0D%0ACl; it takes much more energy to pull an electron away from a valence shell that is nearly full.%0D%0ACl; it takes much more energy to pull an electron away from a valence shell that is nearly full.%0D%0A%0D%0AMg; it takes more energy to pull two electrons away from magnesium(Mg) than it does to take them from chlorine(Cl).%0D%0AMg; it takes more energy to pull two electrons away from magnesium(Mg) than it does to take them from chlorine(Cl).%0D%0A%0D%0ACl; it takes less energy to add an electron to a valence shell that is nearly full.%0D%0ACl; it takes less energy to add an electron to a valence shell that is nearly full.

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.

Chlorine has a higher ionization energy than magnesium because chlorine has seven valence electrons and is one electron short of a full octet, making it energetically favorable to retain those electrons. In contrast, magnesium has two valence electrons which it can lose more easily to achieve a stable electron configuration. Thus, it requires more energy to remove an electron from chlorine than from magnesium.