Electron Configuration for Every Element
This electron configuration tool shows how electrons are arranged in any of the 118 elements, written out subshell by subshell and in shorthand noble gas notation. Select an element and you instantly get its full configuration, orbital diagram, valence electrons, and the quantum numbers of its last electron.
It is built for chemistry students, teachers, and anyone who needs a fast, accurate reference. Configurations follow the Aufbau principle, Pauli exclusion principle, and Hund's rule, and the 20 elements that break the standard filling order are flagged and explained — so you see the real ground-state arrangement, not just the textbook prediction.
How to Find an Electron Configuration
Select an element
Click any cell on the interactive periodic table, type a name, symbol, or atomic number into the search box (for example "Iron", "Fe", or "26"), or step through elements with the Previous/Next buttons or the left and right arrow keys.
Read the results
See the full configuration and noble gas notation, plus the block (s, p, d, or f), valence electron count, unpaired electron count, and the four quantum numbers of the last electron added.
Switch to an ion
Use the Charge selector to move between the neutral atom and its ions (for example Fe²⁺ or Cl⁻). Electrons are added or removed using the correct rules, including removing 4s before 3d for transition metals.
Explore the orbital diagram
Open the Orbital Diagram to see each subshell as a row of boxes. Up and down arrows show electron spin, and the filling follows Hund's rule — one electron per orbital before any orbital pairs up.
Features
Interactive Periodic Table
All 118 elements, color-coded across nine categories from alkali metals to actinides. Click any element to load its configuration.
Full Configuration
The complete electron configuration written subshell by subshell, with subshells color-coded by type for quick reading.
Noble Gas Notation
The condensed shorthand that replaces inner shells with a noble gas core such as [Ar] or [Xe].
Orbital Box Diagram
A visual diagram filling orbitals by Hund's rule, with up and down arrows showing each electron's spin.
Ion Configurations
A Charge selector for cations and anions that applies the correct electron removal and addition order.
20 Flagged Exceptions
Elements that deviate from the Aufbau order carry an Exception badge; tap it to see why, such as half-filled or full d and f stability.
Valence & Unpaired Counts
The number of valence electrons and unpaired electrons, computed for both atoms and ions.
Block Identification
Shows whether the element belongs to the s, p, d, or f block of the periodic table.
Last-Electron Quantum Numbers
The four quantum numbers (n, l, ml, ms) of the last electron added to the configuration.
Search & Keyboard Navigation
Find elements by name, symbol, or atomic number, and step through the table with the left and right arrow keys.
Frequently Asked Questions
How do you write an electron configuration?
Fill subshells in order of increasing energy following the Aufbau principle, place no more than two electrons (with opposite spins) per orbital by the Pauli exclusion principle, and spread electrons out one per orbital before pairing by Hund's rule. This tool does all of that for you — pick an element and it writes the full configuration, for example 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶ for Iron.
What are the Aufbau, Pauli, and Hund rules?
The Aufbau principle says electrons fill the lowest-energy subshells first. The Pauli exclusion principle limits each orbital to two electrons with opposite spins. Hund's rule says electrons occupy separate orbitals of the same subshell singly before any of them pairs up. Together they determine the ground-state arrangement the tool displays, and the orbital diagram shows Hund's rule in action.
What is noble gas (condensed) notation?
Noble gas notation is a shorthand that replaces the inner electrons with the symbol of the nearest preceding noble gas in brackets. For example, Sodium's full configuration 1s² 2s² 2p⁶ 3s¹ becomes [Ne] 3s¹ because the first ten electrons match Neon. The tool shows this condensed form next to the full one for every element.
How do you find the electron configuration of an ion?
Open the Charge selector and choose the ion you want, such as Fe²⁺ or Cl⁻. For cations the tool removes electrons; for anions it adds them. Crucially, for transition metal cations it removes the outer 4s electrons before the 3d electrons, because in a positive ion the 3d orbitals drop below 4s in energy — matching real chemical behavior.
Why do some elements have "Exception" configurations?
About 20 elements, including Chromium and Copper, deviate from the order the Aufbau principle predicts because half-filled or fully filled d and f subshells are especially stable. Chromium is [Ar] 4s¹ 3d⁵ rather than [Ar] 4s² 3d⁴ to gain a half-filled d subshell. These elements carry an Exception badge; tap it to read the reason.
How are valence electrons counted?
For main group elements, valence electrons are those in the highest principal energy level. For transition metals the tool counts both the outermost s electrons and the (n-1)d electrons, since those d electrons take part in bonding. The valence count updates automatically when you switch to an ion.
What do the four quantum numbers mean?
They describe the state of an electron: n (principal) is the shell number; l (azimuthal) is the subshell type (0 = s, 1 = p, 2 = d, 3 = f); ml (magnetic) is the specific orbital, from -l to +l; and ms (spin) is the spin direction, +½ or -½. The tool reports these for the last electron added to the chosen configuration.
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