Electron affinity

Electron affinity is the energy change when a neutral gaseous atom gains an electron to form a negative ion. Its sign and magnitude depend on the convention used and the atom’s electronic structure.

Ionization energy: The energy required to remove an electron from a gaseous atom or ion. It describes the reverse kind of electron transfer, though successive ionization and electron attachment energies are not simple opposites.
Enthalpy: A thermodynamic state function equal to a system’s internal energy plus pressure multiplied by volume. Some tabulated electron affinities report an enthalpy change for electron attachment.
Chemical bonding: The attractive interactions that hold atoms or ions together in molecules and solids. Electron gain energetics contribute to the ionic and covalent bonding patterns of elements.
Electronegativity: A measure of an atom’s tendency to attract shared electrons in a chemical bond. It concerns bonded atoms, whereas electron affinity concerns adding an electron to an isolated gaseous atom.
Effective nuclear charge: The net positive charge experienced by an electron in a multielectron atom after shielding by other electrons. It helps explain how strongly an atom attracts an added electron.
Gibbs free energy: A thermodynamic potential that indicates whether a process is favorable at constant temperature and pressure. Electron affinity is an energy change, not by itself a verdict on whether attachment is spontaneous under all conditions.
Lattice energy: The energy change associated with forming an ionic solid from separated gaseous ions. It can compensate for an unfavorable electron attachment step in the formation of ionic compounds.
Electron-detachment energy: The energy required to remove an electron from a negative ion. It describes the reverse process for a particular anion and is related to, but not always identical with, tabulated affinity conventions.
Electron-electron repulsion: The electrostatic repulsion between negatively charged electrons in an atom or molecule. An added electron can be destabilized by repulsion from electrons already occupying the atom.
Periodic table: A tabular arrangement of chemical elements ordered by atomic number and recurring chemical properties. Electron affinity varies across the table, but the trends include notable exceptions.

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