— Electron configuration notation
Orbital occupancy notation: the number before the letter is the principal quantum number n (the shell), the letter is the subshell type (s, p, d, f), and the superscript is the number of electrons in those orbitals. In 2p⁶, six electrons occupy the second-shell p orbitals. Subshells fill in order of increasing energy (the Aufbau order).
Used in
- Electron configurations
- Periodic trends