Multiplicity in quantum chemistry is used to distinguish between several degenerate wavefunctions that differ only in the orientation of their angular spin momenta. It is defined as 2S+1, where S is the angular spin momentum.
Multiplicity is the quantification of the amount of unpaired electron spin. Multiplicity is a result of Hund's rule which favors the single filling of degenerate (same energy) orbitals. The result is the filling of multiple orbitals with electrons or multiplicity. Multiplicity is calculated with the equation: 2 S + 1 (where S = Σms or more simply put, S = ½(# of unpaired electrons). When all electrons are paired S = 0, and the multiplicity = 2(0) + 1 = 1. This case is called a singlet. If a molecule has 1 unpaired electron S = +½ and 2S + 1 = 2, which is called a doublet. Two unpaired electrons would result in a triplet, etc.
Famous quotes containing the word multiplicity:
“One might get the impression that I recommend a new methodology which replaces induction by counterinduction and uses a multiplicity of theories, metaphysical views, fairy tales, instead of the customary pair theory/observation. This impression would certainly be mistaken. My intention is not to replace one set of general rules by another such set: my intention is rather to convince the reader that all methodologies, even the most obvious ones, have their limits.”
—Paul Feyerabend (1924–1994)