Why does ionization energy generally increase as you move from left to right across a period in the periodic table?

• A. Because atomic radius increases, reducing the attraction between the nucleus and electrons.
• B. Because the number of energy levels increases, making electrons easier to remove.
• C. Because the nuclear charge increases, causing a stronger attraction between the nucleus and valence electrons.
• D. Because the number of valence electrons decreases, making atoms more stable.

Answer: (C)

Verified step by step guidance

1. Understand that ionization energy is the energy required to remove an electron from an atom in its gaseous state.
2. Recognize that as you move from left to right across a period, the number of protons in the nucleus (nuclear charge) increases, while electrons are added to the same principal energy level.
3. Note that the increase in nuclear charge results in a stronger electrostatic attraction between the positively charged nucleus and the negatively charged valence electrons.
4. Since electrons are added to the same energy level, the shielding effect (repulsion from inner electrons) remains relatively constant and does not significantly reduce the increased nuclear attraction.
5. Therefore, the stronger attraction makes it more difficult to remove an electron, causing the ionization energy to generally increase across a period.