Why does carbon (C) have a more exothermic electron affinity than nitrogen (N)?

• A. Because nitrogen is more electronegative than carbon, so it releases more energy when gaining an electron.
• B. Because nitrogen has a larger atomic radius than carbon, making electron addition less favorable.
• C. Because carbon has a higher nuclear charge, which always leads to a less exothermic electron affinity.
• D. Because adding an electron to nitrogen results in electron-electron repulsion due to its half-filled 2p subshell.

Answer: (D)

Verified step by step guidance

1. Understand that electron affinity (EA) is the energy change when an atom gains an electron, typically releasing energy (exothermic) if the atom stabilizes upon gaining the electron.
2. Recall the electron configurations: Carbon (C) has the configuration 1s\^2 2s\^2 2p\^2, while Nitrogen (N) has 1s\^2 2s\^2 2p\^3, which is a half-filled 2p subshell.
3. Recognize that half-filled subshells, like nitrogen's 2p\^3, are particularly stable due to electron exchange energy and symmetry, making the addition of an extra electron less favorable.
4. Consider that adding an electron to nitrogen forces pairing in one of the 2p orbitals, causing increased electron-electron repulsion, which reduces the energy released (less exothermic EA).
5. In contrast, carbon's 2p\^2 configuration allows the added electron to occupy an empty 2p orbital without pairing, resulting in a more stable configuration and a more exothermic electron affinity.