Which of the following elements has the highest (most negative) electron affinity?

• A. Na
• B. Ne
• C. Cl
• D. O

Answer: (C)

Verified step by step guidance

1. Understand that electron affinity is the energy change that occurs when an atom gains an electron, typically measured in kJ/mol. A more negative value means the atom releases more energy and has a higher tendency to gain an electron.
2. Recall the general trend of electron affinity in the periodic table: it tends to increase (become more negative) across a period from left to right and decrease down a group.
3. Analyze the given elements: Na (sodium) is an alkali metal in Group 1, Ne (neon) is a noble gas in Group 18, Cl (chlorine) is a halogen in Group 17, and O (oxygen) is a chalcogen in Group 16.
4. Recognize that halogens like Cl have high (more negative) electron affinities because they are one electron short of a full octet, making them very eager to gain an electron.
5. Conclude that among the given elements, Cl has the highest (most negative) electron affinity due to its position in the periodic table and its electronic configuration.