Choose the element with the more negative (more exothermic)...

Choose the element with the more negative (more exothermic) electron affinity from each pair.
a. $\mathrm{Mg}$ or $\mathrm{S}$
b. $\mathrm{Kor} \mathrm{Cs}$
c. $\mathrm{Si}$ or $\mathrm{P}$
d. Ga or Br

Key Concepts

Atomic Structure and Electron Configuration

The electron configuration of an atom plays a crucial role in determining its electron affinity. Atoms that are close to having a filled or half-filled valence shell tend to release more energy upon gaining an electron, as this leads to a more stable and energetically favorable electron configuration. Structural factors, such as electron-electron repulsion in nearly full subshells, can also influence the observed electron affinity.

Exothermic Process in Electron Addition

When electron affinity is described as exothermic, it implies that the process of adding an electron to an atom releases energy. The more negative the electron affinity value, the greater the energy released, which indicates a more favorable electron uptake process.

Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. It is a quantitative measure of an atom's tendency to accept an electron, and when this process is exothermic, it means that energy is released, indicating a strong attraction between the atom and the additional electron.

Periodic Trends in Electron Affinity

Across the periodic table, electron affinity generally becomes more exothermic (more negative) from left to right within a period due to increasing effective nuclear charge, which makes an atom more attracted to additional electrons. Conversely, electron affinity typically becomes less exothermic (less negative) as one moves down a group, due to the increasing atomic radius and the greater distance between the nucleus and the added electron.

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