Which of the following best describes the trend in ionization energy as you move from left to right across a period in the periodic table?

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

Answer: (C)

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 from left to right across a period in the periodic table, the nuclear charge (number of protons) increases while the electron shielding remains relatively constant.
3. Recognize that the increasing nuclear charge pulls the electrons closer to the nucleus, making it harder to remove an electron.
4. Conclude that because of the stronger attraction between the nucleus and the electrons, the ionization energy generally increases across a period.
5. Note that this trend is consistent and does not typically show a decrease or remain constant across a period.