Use our electron configuration calculator for quick and accurate calculations. Free online tool.
The Electron Configuration Calculator determines how electrons are distributed among the atomic orbitals of any element. By entering an atomic number or element symbol, you instantly receive the full ground-state electron configuration written in standard spdf notation, such as 1s²2s²2p⁶3s²3p⁶ for argon. The tool applies the Aufbau principle, Pauli exclusion principle, and Hund's rule to fill orbitals in the correct order.
Electrons fill orbitals following the Aufbau (building-up) order: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p. For example, iron (Fe, Z=26) has the configuration 1s²2s²2p⁶3s²3p⁶3d⁶4s², because the 4s subshell fills before 3d, and the six 3d electrons spread across orbitals to maximize spin according to Hund's rule.
Accepted inputs include atomic numbers from 1 to 118 or standard element symbols (e.g., H, Fe, Au). The calculator outputs the full ground-state configuration, identifies the valence electrons, and flags any exceptions to the Aufbau rule (such as Cr and Cu). It is used by chemistry students, educators, and researchers studying periodic trends, chemical bonding, and spectroscopy.
Electron configuration, orbital diagrams, valence electrons, and electron arrangement
Explore CategoryThe Aufbau principle states that electrons occupy the lowest available energy orbital first. Orbitals are filled in order of increasing energy, following the n + l rule for subshell ordering.
Chromium (Z=24) adopts [Ar]3d⁵4s¹ and copper (Z=29) adopts [Ar]3d¹⁰4s¹ because half-filled and fully filled d subshells provide extra stability that overrides the standard Aufbau order.
The superscript indicates the number of electrons in that subshell. For example, 2p⁶ means the 2p subshell contains six electrons, which is its maximum capacity.
The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers, meaning each orbital holds at most two electrons with opposite spins.
An s subshell holds 2 electrons, a p subshell holds 6, a d subshell holds 10, and an f subshell holds 14 electrons, based on the number of orbitals (2l+1) each subshell contains.