Electron affinity

The electron affinity measure the ability of a neutral atom to gain an electron, as described by the reaction:

$${\rm X} + e^- \longrightarrow X^-$$

The electron affinity, $EA$ is defined to be the negative of $\Delta E$ for this reaction:

$$EA = -\Delta E = E({\rm reactants}) -E({\rm products})$$

$EA$ can be either positive or negative. If $EA>0$, attachment is stable. If $EA<0$, attachment is unstable, and the electron must be forced to stick to the atom.