Parity (physics) of formula_59, The overall parity of a many-particle system is the product of the parities of the one-particle states. It is -1 if an odd number of particles are in odd-parity states, and +1 otherwise. Different notations are in use to denote the parity of nuclei, atoms, and molecules. Atomic orbitals have parity (-1), where the exponent ℓ is the azimuthal quantum number. The parity is odd for orbitals p, f, ... with ℓ = 1, 3, ..., and an atomic state has odd parity if an odd number of electrons occupy these orbitals. For example, the ground state of
Electron affinity Electron affinity In chemistry and atomic physics, the electron affinity ("E") of an atom or molecule is defined as the amount of energy "released" or "spent" when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion. In solid state physics, the electron affinity for a surface is defined somewhat differently (see below). This property is measured for atoms and molecules in the gaseous state only, since in a solid or liquid state their energy levels would be changed by contact with other atoms or molecules. A list of the electron