Question

the reaction for electron affinity for several elements is given. which element would have the most favorable electron affinity?
kr + e⁻ → kr⁻
he + e⁻ → he⁻
c + e⁻ → c⁻
be + e⁻ → be⁻

Explanation:

Electron affinity is the energy change when an electron is added to a neutral atom; a more favorable (more negative) value means the atom readily accepts an electron. Noble gases (Kr, He) have full valence shells, so adding an electron is highly unfavorable (positive energy). Beryllium (Be) has a filled 2s orbital, so adding an electron requires energy (unfavorable). Carbon (C) has a half-filled 2p subshell and readily accepts an electron to reach a more stable configuration, resulting in a favorable (negative) electron affinity.

Answer:

C. $\text{C} + \text{e}^-
ightarrow \text{C}^-$