Spin (physics) Spin (physics) In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei. Spin is one of two types of angular momentum in quantum mechanics, the other being "orbital angular momentum". The orbital angular momentum operator is the quantum-mechanical counterpart to the classical angular momentum of orbital revolution and appears when there is periodic structure to its wavefunction as the angle varies. The existence of spin angular momentum is inferred from experiments, such as the Stern–Gerlach experiment, in which silver atoms were observed to possess two possible
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