What is the trend for ionization energy as you go down a group on the periodic table?

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

Answer: (C)

Verified step by step guidance

1. Recall that ionization energy is the energy required to remove an electron from a gaseous atom or ion.
2. Understand that as you move down a group in the periodic table, atoms have more electron shells, increasing the distance between the nucleus and the outermost electron.
3. Recognize that increased distance and additional inner electron shells cause greater electron shielding, which reduces the effective nuclear charge felt by the outermost electron.
4. Since the outermost electron is held less tightly due to shielding and increased distance, less energy is required to remove it, meaning ionization energy decreases.
5. Therefore, the trend for ionization energy as you go down a group is a decrease in ionization energy.