Video Transcript
In general, how does electron affinity change when going down groups one, 14, 16, and 17 of the periodic table? (A) It increases, (B) it stays the same, (C) it decreases, or (D) it alternates between increasing and decreasing.
The electron affinity of an element is the energy released when an electron is added to a neutral atom in the gas state to form a negative ion. Electron affinity is affected by atomic radius, with larger atoms often having lower electron affinities relative to other elements in the same group. This is because the electron being added to a larger atom is farther from the attractive forces of the nucleus. Therefore, the stronger the attraction between the electrons and the nucleus, the more energy is released when an electron is gained and the higher the electron affinity.
So for groups one, 14, 16, and 17, as we go down the groups and see an increase in atomic radius, we see that electron affinity decreases. For example, the first element in group 17 has an electron affinity of 328 kilojoules per mole, while the last element has an electron affinity of 166 kilojoules per mole. It is worth noting that while we do see an overall decrease in electron affinity down a group, there are some anomalies present in groups 16 and 17. Therefore, in general, electron affinity changes going down groups one, 14, 16, and 17 of the periodic table as described by answer choice (C). It decreases.
