Which statement best describes the electron affinity trends for noble gases and halogens on the periodic table?

• A. Both halogens and noble gases have high (negative) electron affinities.
• B. Noble gases have higher electron affinities than halogens.
• C. Halogens and noble gases both have electron affinities close to zero.
• D. Halogens have high (negative) electron affinities, while noble gases have very low (positive or near zero) electron affinities.

Answer: (D)

Verified step by step guidance

1. Understand that electron affinity refers to the energy change when an atom gains an electron, typically measured in kJ/mol. A high (negative) electron affinity means the atom releases energy when gaining an electron, indicating a strong tendency to accept an electron.
2. Recall the position of halogens and noble gases on the periodic table: halogens are in Group 17, one electron short of a full valence shell, while noble gases are in Group 18, with a full valence shell.
3. Recognize that halogens have high (negative) electron affinities because they readily gain an electron to achieve a stable octet, releasing energy in the process.
4. Understand that noble gases have very low or positive electron affinities because their valence shells are already full, so adding an electron is energetically unfavorable or requires energy input.
5. Conclude that the correct description is that halogens have high (negative) electron affinities, while noble gases have very low (positive or near zero) electron affinities, reflecting their differing tendencies to gain electrons.