fsubniveau

Fsubniveau, sometimes written f-sublevel or f-subshell, is the set of atomic orbitals with orbital angular momentum quantum number l = 3 in quantum mechanics. Within a given principal shell n, there are seven f orbitals corresponding to magnetic quantum numbers m_l = -3, -2, -1, 0, 1, 2, 3. Each orbital can accommodate two electrons with opposite spins, giving a maximum of 14 electrons for a single f-sublevel when it is present.

In atomic structure, f-sublevels are relatively narrow in energy and are highly shielded by inner electron shells. They typically appear in the heavier elements and play a key role in the chemistry of the lanthanides and actinides. The 4f subshell is filled in the lanthanide series, while the 5f subshell is involved in the chemistry of the actinide series. The energy ordering of f-sublevels can vary across elements due to electron–electron repulsion, screening, and relativistic effects, leading to deviations from simple orbital fill rules.

The presence of f-sublevels influences spectral and magnetic properties. Transitions involving f orbitals contribute to characteristic lines in the spectra of lanthanides and actinides, and f-electron configurations give rise to rich multiplet structures described by term symbols. Spin–orbit coupling splits individual f levels into distinct total angular momentum states, with possible j-values determined by j = l ± s (for a single electron, j = 7/2 or 5/2).

Overall, the f-sublevel is a fundamental component of the electronic structure in heavier elements, associated with a distinctive set of orbitals, high angular momentum, and notable roles in spectroscopy and magnetism.