# Unsöld's Theorem

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A theorem due to A. Unsöld, *Ann. Physik,* 82, 1927 pp. 355-365 states that a filled or half-filled subshell of atomic orbitals with is spherically symmetrical and thus contributes an orbital angular momentum of zero. This can be illustrated by evaluating the sum of atomic orbital densities , or equivalently , giving a spherically symmetrical function (independent of and ). The nitrogen atom in its ground state has the configuration …, with three electrons of parallel spins singly occupying the three degenerate -orbitals. Neon has a completely filled subshell with configuration …. Likewise, the half-filled subshells in Cr and Mn lead to spherically symmetrical ground states. The mathematical proof of Unsöld's theorem follows from the spherical-harmonic identity

Contributed by: S. M. Blinder (March 2011)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

Snapshot 1: a configuration, showing a orbital hole

Snapshot 2: spherically symmetrical or configuration

Snapshot 3: configuration, which accounts for square-planar complexes of Ni, Pd and Pt

## Permanent Citation