Which of the following best explains why successive ionization energies increase for an atom?

• A. The atom gains electrons after each ionization, increasing repulsion and energy required.
• B. With each electron removed, the remaining electrons experience a stronger effective nuclear charge, making it harder to remove the next electron.
• C. Each successive electron is farther from the nucleus, so it requires more energy to remove.
• D. Successive ionization energies decrease because the atom becomes more stable after each electron is removed.

Answer: (B)

Verified step by step guidance

1. Understand what ionization energy means: it is the energy required to remove an electron from an atom or ion in the gaseous state.
2. Recognize that when an electron is removed, the atom becomes a positively charged ion, which affects the attraction between the nucleus and the remaining electrons.
3. Recall the concept of effective nuclear charge (Z_eff), which is the net positive charge experienced by an electron after accounting for shielding by other electrons.
4. With each successive electron removed, the number of electrons decreases while the number of protons in the nucleus remains the same, so the effective nuclear charge experienced by the remaining electrons increases.
5. Because the remaining electrons feel a stronger pull from the nucleus, more energy is required to remove the next electron, which explains why successive ionization energies increase.