In quantum chemistry, Slater's rules provide numerical values for the effective nuclear charge in a many-electron atom.
[1] Revised values of screening constants based on computations of atomic structure by the Hartree–Fock method were obtained by Enrico Clementi et al. in the 1960s.
Specifically, for each electron in an atom, Slater wished to determine shielding constants (s) and "effective" quantum numbers (n*) such that provides a reasonable approximation to a single-electron wave function.
[5] Slater argued on the basis of previous calculations by Clarence Zener[6] that the presence of radial nodes was not required to obtain a reasonable approximation.
Slater then argued, again based on the work of Zener, that the total energy of a N-electron atom with a wavefunction constructed from orbitals of his form should be well approximated as Using this expression for the total energy of an atom (or ion) as a function of the shielding constants and effective quantum numbers, Slater was able to compose rules such that spectral energies calculated agree reasonably well with experimental values for a wide range of atoms.