Electron Configuration Calculator
Select any element to instantly get its full electron configuration, noble gas notation, valence electrons, atomic mass, period, and group.
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Aufbau principle: Electrons fill lowest energy orbitals first
Pauli exclusion: Max 2 electrons per orbital (opposite spins)
Hund's rule: Electrons fill empty orbitals before pairing
Full Configuration
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Noble Gas Notation
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Valence Electrons
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Subshell Filling
Search for an element and click Get Electron Configuration to see the results.
Aufbau Filling Order
1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p
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What is Electron Configuration?
Electron configuration describes how electrons are arranged in an atom's orbitals. It is written by listing each subshell followed by the number of electrons in it as a superscript (e.g., 1s² 2s² 2p³ for nitrogen).
The noble gas notation (abbreviated form) replaces the core electrons with the symbol of the nearest noble gas in brackets, making it quicker to write (e.g., [He] 2s² 2p³ for nitrogen).
Valence electrons are those in the outermost shell (beyond the noble gas core). They determine an element's chemical reactivity and how it forms bonds.
The Three Rules of Electron Configuration
Aufbau Principle
Electrons fill the lowest available energy level first, following the diagonal rule order: 1s, 2s, 2p, 3s, 3p, 4s, 3d…
Pauli Exclusion Principle
No two electrons in the same atom can have the same set of four quantum numbers. Each orbital holds at most 2 electrons with opposite spins.
Hund's Rule
Electrons occupy all available orbitals of the same energy singly before any orbital is doubly occupied. Paired electrons have opposite spins.
Frequently Asked Questions
Why does Chromium have an anomalous configuration?
Chromium ([Ar] 3d⁵ 4s¹) and copper ([Ar] 3d¹⁰ 4s¹) are exceptions to the Aufbau rule. A half-filled (3d⁵) or fully-filled (3d¹⁰) d subshell provides extra stability due to exchange energy, so one electron "moves" from 4s to 3d.
What are valence electrons and why do they matter?
Valence electrons are in the outermost electron shell. They participate in forming chemical bonds and determine reactivity. Elements in the same group have the same number of valence electrons and similar chemical behavior.
What do s, p, d, f blocks mean?
The block refers to the highest-energy orbital type being filled. s-block: groups 1–2; p-block: groups 13–18; d-block: transition metals (groups 3–12); f-block: lanthanides and actinides.
How do I write abbreviated (noble gas) notation?
Find the noble gas that comes just before the element in the periodic table. Write its symbol in brackets, then write the remaining electron configuration. For example, Phosphorus (Z=15) = [Ne] 3s² 3p³.