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Electron Configuration Generator

Enter any element by name, symbol, or atomic number to see its full electron configuration, noble gas shorthand, orbital box diagram, and valence electron count.

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Results

Element
Iron (Fe)
Atomic Number
26
Full Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
Noble Gas Shorthand
[Ar] 4s² 3d⁶
Block
D-block
Period
4
Group
8
Valence Electrons
8
Common Oxidation States
+2, +3

Orbital Diagram

1s↑↓2e⁻2s↑↓2e⁻2p↑↓↑↓↑↓6e⁻3s↑↓2e⁻3p↑↓↑↓↑↓6e⁻4s↑↓2e⁻3d↑↓↑↑↑↑6e⁻
s-orbitalp-orbitald-orbitalf-orbital

Step-by-Step

1. Identify the element

Iron (Fe), Z=26\text{Iron (Fe), } Z = 26

2. Fill orbitals following the Aufbau principle

Order: 1s→2s→2p→3s→3p→4s→3d→4p→⋯\text{Order: } 1s \to 2s \to 2p \to 3s \to 3p \to 4s \to 3d \to 4p \to \cdots

3. Write the full electron configuration

1s2 2s2 2p6 3s2 3p6 4s2 3d61s^{2}\,2s^{2}\,2p^{6}\,3s^{2}\,3p^{6}\,4s^{2}\,3d^{6}

4. Noble gas shorthand

[Ar] 4s² 3d⁶\text{[Ar] 4s² 3d⁶}

5. Identify valence electrons

Valence electrons=8\text{Valence electrons} = 8

Reference Guide

Aufbau Principle

Electrons fill orbitals from lowest to highest energy. The filling order follows increasing (n + l) values.

1s→2s→2p→3s→3p→4s→3d→⋯1s \to 2s \to 2p \to 3s \to 3p \to 4s \to 3d \to \cdots

Hund's Rule

Electrons occupy orbitals singly before pairing up. Each orbital in a subshell gets one electron (with parallel spin) before any orbital gets a second.

Exceptions (Cr, Cu)

Chromium and copper deviate from the expected filling order because half-filled and fully filled d subshells provide extra stability.

Cr: [Ar] 3d5 4s1Cu: [Ar] 3d10 4s1\text{Cr: [Ar] } 3d^5\,4s^1 \quad \text{Cu: [Ar] } 3d^{10}\,4s^1

Noble Gas Shorthand

The core electrons can be abbreviated using the nearest noble gas with a lower atomic number in square brackets.

Fe: [Ar] 3d6 4s2\text{Fe: } [\text{Ar}]\,3d^6\,4s^2