⚛️ Electron Configuration Calculator
Enter an atomic number to see the element’s ground-state electron configuration, built up shell by shell with the Aufbau principle.
What This Calculator Does
This tool builds the ground-state electron configuration for any element from its atomic number (Z), showing how its electrons are distributed across shells and subshells.
The Method
Electrons fill orbitals in order of increasing energy, following the Aufbau principle (the standard filling order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p). Each subshell holds a maximum number of electrons (s = 2, p = 6, d = 10, f = 14). The calculator fills each subshell in turn until all Z electrons are placed, then reports the configuration along with the electrons in the outermost occupied shell (a common working definition of valence electrons).
A Few Notes
- A small number of elements (such as chromium and copper) have experimentally observed configurations that deviate slightly from the strict Aufbau order due to extra stability from half-filled or fully-filled d subshells; this calculator uses the standard Aufbau prediction, which is correct for the large majority of elements and is the version taught in introductory chemistry.
- For transition metals, the “valence electron” count shown reflects the outermost shell only and may differ from the number of electrons actually involved in bonding.
- Intended for general chemistry education and reference purposes.