What does electron affinity measure?

Electron affinity measures the energy change that occurs when an atom in the gas phase gains an electron, leading to the formation of a negatively charged ion. When an atom attracts and captures an electron, energy is often released during this process. This release of energy is indicative of how much an atom "wants" an additional electron, and it reflects the stability and reactivity of the atom in question.

For various elements, electron affinity can vary significantly. Atoms with high electron affinities, like halogens, release substantial amounts of energy when they gain an electron, making them highly reactive. Conversely, elements that do not favor gaining electrons, such as noble gases, exhibit lower electron affinities.

Understanding electron affinity is crucial for grasping concepts related to atomic structure and chemical bonding, as it plays a significant role in predicting how and why atoms interact with one another.