Which element has the highest electron affinity among the following, unlike electronegativity trends where fluorine is typically highest?

Which element has the highest electron affinity among the following, unlike electronegativity trends where fluorine is typically highest?

• A. Fluorine
• B. Oxygen
• C. Neon
• D. Chlorine

Answer: (D)

Electron affinity is the energy change when an atom in the gas phase gains an electron; a more negative value means the atom more readily accepts an electron. Halogens are highly eager to complete their octet, so they tend to have large, negative electron affinities. Among the given elements, chlorine releases the most energy upon gaining an electron. Fluorine, while highly electronegative, is very small, and the added electron experiences significant repulsion in the compact 2p orbitals, which slightly reduces the energy released. Oxygen also gains electrons readily, but its first electron affinity is less exothermic than chlorine’s because of its orbital arrangement and electron–electron repulsion patterns. Neon, with a complete outer shell, has little to no tendency to accept an electron, making its electron affinity effectively negligible. Thus chlorine has the highest electron affinity among the options.

Electron affinity is the energy change when an atom in the gas phase gains an electron; a more negative value means the atom more readily accepts an electron. Halogens are highly eager to complete their octet, so they tend to have large, negative electron affinities. Among the given elements, chlorine releases the most energy upon gaining an electron. Fluorine, while highly electronegative, is very small, and the added electron experiences significant repulsion in the compact 2p orbitals, which slightly reduces the energy released. Oxygen also gains electrons readily, but its first electron affinity is less exothermic than chlorine’s because of its orbital arrangement and electron–electron repulsion patterns. Neon, with a complete outer shell, has little to no tendency to accept an electron, making its electron affinity effectively negligible. Thus chlorine has the highest electron affinity among the options.