In quantum chemistry, a configuration state function (CSF), is a symmetry-adapted linear combination of Slater determinants. It is an eigenstate of the square of the angular momentum operator and of the square of spin operator . A CSF must not be confused with a configuration. Linus Pauling, as a pioneer of the valence bond theory, is one of the first quantum chemists. ... A Slater determinant (named after the physicist John C. Slater) is an expression in quantum mechanics for the wavefunction of a many-fermion system, which by construction satisfies the Pauli principle. ... Electron atomic and molecular orbitals In atomic physics and quantum chemistry, the electron configuration is the arrangement of electrons in an atom, molecule or other body. ...