2p1

2p1 is a terse designation used mainly in atomic physics and chemistry. It is commonly read as a shorthand for the electronic configuration 2p^1, indicating that one electron occupies the 2p subshell (the n = 2, l = 1 level). In a simple one-electron picture this corresponds to a single valence electron in a 2p orbital; in many-electron atoms it forms part of a larger configuration, such as [He] 2s^2 2p^1, which occurs in elements like boron and in certain ions.

When a single electron is in a p subshell, its possible term symbols arise from the coupling of orbital and spin angular momenta. For a p^1 configuration the spectroscopic term is a 2P term, which splits by spin-orbit interaction into two fine-structure levels with total angular momentum J = 1/2 and J = 3/2, typically written as 2P1/2 and 2P3/2 in detailed spectroscopic notations. Transitions involving these states follow selection rules that govern visible and ultraviolet spectral lines in laboratory and astronomical spectra.

In practical terms, 2p^1 commonly appears in the ground-state configuration of boron and in ions with a similar valence structure. It also serves as a reference point for discussing electron correlation effects and term splitting in second-shell p-block elements. The notation is less often used as a standalone object name; instead, it is part of broader descriptions of atomic configurations, energy levels, and spectral lines.

See also: electron configuration, p subshell, term symbol, fine structure.