Which of the following best describes the trend in ionization energy as you move from left to right across period 2 of the periodic table?

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

Answer: (D)

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 electrons are added to the same principal energy level.
3. Recognize that the increasing nuclear charge causes a stronger attraction between the nucleus and the electrons, making it harder to remove an electron.
4. Note that the shielding effect remains relatively constant across a period because electrons are added to the same shell, so it does not significantly offset the increased nuclear charge.
5. Conclude that due to the stronger attraction and relatively constant shielding, the ionization energy generally increases from left to right across period 2.