As you move down a group in the periodic table, what happens to the ionization energy of the elements?

• A. Ionization energy first increases, then decreases
• B. Ionization energy decreases
• C. Ionization energy remains constant
• D. Ionization energy increases

Answer: (B)

Verified step by step guidance

1. Understand that ionization energy is the energy required to remove an electron from a gaseous atom or ion.
2. Recall that as you move down a group in the periodic table, the atomic radius increases because additional electron shells are added.
3. Recognize that the increased distance between the nucleus and the outermost electron reduces the effective nuclear charge experienced by that electron.
4. Consider that increased electron shielding from inner shells further decreases the attraction between the nucleus and the outermost electron.
5. Conclude that because of the larger atomic radius and increased shielding, the ionization energy decreases as you move down a group.