Which of the following elements has the most negative electron affinity?

• A. Cl
• B. Na
• C. O
• D. Ne

Answer: (A)

Verified step by step guidance

1. Understand that electron affinity (EA) is the energy change when an atom gains an electron; a more negative value means the atom releases more energy and more readily accepts an electron.
2. Recall that electron affinity generally becomes more negative across a period from left to right in the periodic table, due to increasing nuclear charge attracting the added electron more strongly.
3. Consider the elements given: Na (Group 1), O (Group 16), Cl (Group 17), and Ne (Group 18). Noble gases like Ne have very low or positive electron affinities because their electron shells are full and stable.
4. Recognize that halogens (Group 17), such as Cl, typically have the most negative electron affinities because they are one electron short of a full octet and strongly attract an additional electron.
5. Conclude that among the options, Cl has the most negative electron affinity due to its position in the periodic table and its tendency to gain an electron to complete its valence shell.