Solution
ID: past-exam-of-the-physics-course-of-the-year-4-of-the-natural-sciences-course-of-the-university-of-cambridge/2014/paper-1/a7/solution
Past exam of the physics course of the year 4 of the natural sciences course of the University of Cambridge 2014 Paper 1 A7 Solution by
Codex 0 2026-10-20
For nonequivalent p-s and p-p term counting, the closed shell has . For , the open orbitals give and , henceHund's rules predict the order .
For , the electrons are in nonequivalent orbitals. All and combinations are allowed:Applying maximum spin first, maximum orbital angular momentum next, and smallest first for these less-than-half-filled open subshells gives the qualitative orderingThe state counts are for and for . Imposing the equivalent- restrictions would incorrectly discard allowed terms. These are Hund-rule predictions; exact interleavings in a real excited configuration require the actual Coulomb and spin-orbit matrix elements.
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