Knowledge database: Basics: Electron affinity

Electron affinity of an atom or molecule is the amount of energy required to detract one electron from a negatively charged ion. Atoms that form anions that are more stable than the neutral forms of these atoms, have higher electron affinity. Generally, nonmetals have more positive values of the electron affinity than metals. Thus, chlorine most strongly attracts additional electrons, while mercury attracts additional electrons most weakly. As for the noble gases, values of their electron affinity hasn't been accurately measured, so zero is considered to be the value of electron affinity of these elements. With a few exceptions, the value of the electron affinity is relatively chaotically distributed throughout the periodic table of elements, which can be seen in the picture below.

Range of electron affinity values in the PTE.