4f14

4f14 is a shorthand used in atomic physics and inorganic chemistry to denote a completely filled 4f subshell, meaning the 4f orbitals collectively hold 14 electrons (the maximum for an f subshell, since there are seven f orbitals each able to hold two electrons).

This configuration occurs in certain elements and oxidation states. In neutral ytterbium (Yb, atomic number 70), the ground-state electron configuration is [Xe] 4f14 6s2. In the doubly charged cation Yb2+, the configuration remains [Xe] 4f14, illustrating how the 4f shell can be fully occupied despite changes in the outer electrons. Lutetium (Lu) also features 4f14 as part of its ground-state arrangement, described in some references as [Xe] 4f14 5d1 6s2, highlighting the close energetic proximity of the 4f, 5d, and 6s subshells in the later lanthanides.

Significance: a filled 4f subshell provides strong shielding of core electrons and tends to make the chemistry of species with a 4f14 core largely governed by outer-shell electrons, a hallmark of the lanthanide series. The 4f electrons themselves contribute little to bonding in many contexts, and spectral transitions involving the 4f subshell are often limited or involve outer-shell processes rather than 4f-4f transitions, which are not available when the 4f shell is full.

See also: f-block elements, lanthanides, electron configuration, ytterbium.