4f6

4f6 denotes an occupancy of six electrons in the 4f subshell of an atom. It is most commonly discussed in the context of the lanthanide series, where the 4f block contains electrons that are partially shielded by outer shells. In neutral samarium, the ground-state electron configuration is [Xe] 4f6 6s2, illustrating how the 4f6 arrangement appears in practical chemistry and spectroscopy.

In chemical and solid-state contexts, the 4f electrons are relatively tightly bound and shielded by the filled 5s and 5p shells. This shielding leads to similarities in chemical behavior across the lanthanide series, while the 4f occupancy can influence magnetic and spectroscopic properties. For samarium, the 4f6 configuration is also relevant in its divalent state (Sm2+), where the configuration is often described as [Xe] 4f6. In the trivalent state (Sm3+), the configuration becomes 4f5, reflecting common oxidation-state trends in samarium compounds.

Spectroscopically, 4f electrons give rise to rich multiplet structures and relatively sharp f-f transitions, due to their shielding-dominated interactions. This underpins the use of lanthanide-doped materials in phosphors and lasers, as well as the appearance of characteristic absorption and emission lines associated with 4f6 configurations in certain ions and compounds.

Samarium itself is a rare earth element with prominent applications in permanent magnets (notably SmCo-based magnets), phosphors, catalysts, and specialty materials. The 4f6 occupancy is a key aspect of understanding its magnetic behavior and its role in various solid-state and optical applications.