Electron Configuration Calculator

Electron Configuration Calculator

The Electron Configuration Calculator shows how electrons fill atomic orbitals for any element from hydrogen ($Z = 1$) through oganesson ($Z = 118$). It returns full notation, noble-gas shorthand, and valence electron count.

Electrons fill subshells in order of increasing energy (aufbau principle):

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d \rightarrow 4p \rightarrow \ldots$$

For example, nitrogen ($Z = 7$) has configuration $1s^2 2s^2 2p^3$, shorthand $[\text{He}]\,2s^2 2p^3$, and five valence electrons in the outer $n = 2$ shell. Copper ($Z = 29$) is an exception: one $4s$ electron moves to $3d$ for stability, giving $[\text{Ar}]\,4s^1 3d^{10}$.

Related tools: Effective Nuclear Charge Calculator and Electronegativity Calculator.