What is the energy change called when a neutral atom gains an electron?
nuclear fission
fusion gain
mass affinity
electron affinity
The energy change that occurs when a neutral atom gains an electron is called its electron affinity . When energy is released in a chemical reaction or process, that energy is expressed as a negative number. The figure below shows electron affinities in kJ/mole for the representative elements. Electron affinities are measured on atoms in the gaseous state and are very difficult to measure accurately.