Why does ionization energy decrease as you go down a group on the periodic table?

• A. Because the outer electrons are farther from the nucleus and experience greater shielding, making them easier to remove.
• B. Because the nuclear charge decreases as you go down a group, reducing the attraction to electrons.
• C. Because atoms gain more protons, which makes it harder to remove electrons.
• D. Because the number of valence electrons increases, making the atom more stable.

Answer: (A)

Verified step by step guidance

1. Understand that ionization energy is the energy required to remove an electron from an atom in its gaseous state.
2. Recognize that as you move down a group in the periodic table, atoms have more electron shells, so the outermost electrons are located farther from the nucleus.
3. Know that the inner electrons between the nucleus and the outermost electrons create a shielding effect, which reduces the effective nuclear charge felt by the outer electrons.
4. Because of this increased distance and shielding, the attraction between the nucleus and the outermost electrons decreases, making it easier to remove these electrons.
5. Therefore, ionization energy decreases down a group due to the combined effects of increased atomic radius and greater electron shielding.