Electron Configuration Calculator

01 Set up your calculation

1. Select a neutral element, or switch to atomic number and enter a whole number from 1 to 108. The supported range runs from hydrogen to hassium.
2. Read the shorthand and full configurations. A count following a subshell gives its electrons: 3d6 means six electrons in 3d. The output includes explicit 1s1 or 4s1 counts where needed.
3. Use the shell populations to check the total against Z. The highest-shell count is a shell count, not a universal valence-electron count. Check the reference-status row for predicted heavy-element entries.

02 The relationship

For the assumptions behind these results, read the explanation below. You can also explore Effective Nuclear Charge and Atom.

03 Read a subshell count and expand its core

In 3d6, the leading 3 identifies the principal shell, d identifies the subshell, and the final 6 is the electron count. The s, p, d and f capacities differ because those subshells contain different numbers of orbitals. Listing an occupied subshell does not mean that every orbital in it is filled.

A bracketed noble-gas symbol replaces its complete configuration. In iron’s [Ar] 3d6 4s2, the argon core accounts for 18 electrons. Six 3d and two 4s electrons bring the total to 26. The calculator uses the largest preceding noble-gas core; hydrogen and helium have no shorter core abbreviation.

04 Use the reference arrangement beyond a filling diagram

A diagonal filling diagram is useful for learning the usual progression, but neighboring subshells can be close in energy. The neutral configurations listed here retain the reference exceptions. Chromium is [Ar] 3d5 4s1, copper is [Ar] 3d10 4s1, and palladium is [Kr] 4d10.

The display groups subshells by increasing principal shell, then s, p, d and f. This order makes the shell totals easy to check; it is not a proposed sequence of electron addition. A text that writes 4s before 3d can describe the same occupation numbers.

05 Distinguish the outer shell from chemical valence

The highest occupied shell is the largest n that contains electrons in the listed configuration. Its electron count is a direct sum. For iron, that means the two 4s electrons; the six 3d electrons belong to n = 3 even though d electrons also matter in transition-metal chemistry.

Palladium illustrates why this definition needs care. Its neutral reference configuration has no 5s electrons, so n = 4 is its highest occupied shell. That shell contains 4s2, 4p6 and 4d10, totaling 18. This does not mean palladium forms 18 ordinary chemical bonds.

06 Keep the neutral-atom scope in view

These entries describe isolated neutral atoms and their listed lowest-energy configurations. They are not ion configurations, molecular orbitals or arrangements in a crystal. A positive ion can rearrange when electrons are removed; a neutral lookup cannot establish the ground state of every ion.

The available reference set covers Z = 1–108. Entries for 104–108 are labeled predicted, and a reference label for lighter entries is not a claim that every orbital population has been measured directly. The references include lawrencium as [Rn] 5f14 7s2 7p1. Elements 109–118 are outside this calculator’s verified data coverage.