Use the electron configuration calculator to find full and noble-gas shorthand notation, orbital diagrams, valence electrons, shell distribution.
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Build an electron configuration from an element or ion Type an element name, symbol, or atomic number to generate the full configuration, noble-gas shorthand, shell distribution, valence view, and an orbital-diagram-style filling trace.
Quick examples
Assumptions
Neutral atoms use known ground-state exceptions where this page lists them. Cations remove electrons from the highest principal shell first, while anions add electrons through the standard filling order. Excited states and term symbols are outside this calculator.
Enter an element Add an element name, symbol, or atomic number from 1 to 118 to calculate the electron configuration and orbital filling.
Electron configuration calculator guide: Aufbau order, orbital diagrams
Electron configuration describes how electrons occupy atomic orbitals in the ground state of an atom or simple ion. This electron configuration calculator builds the full configuration, noble-gas shorthand, shell distribution, valence-shell view, and orbital-diagram-style filling trace from an element name, symbol, or atomic number while also flagging common neutral-atom exceptions that do not follow the simple Aufbau order exactly.
What electron configuration is showing
An electron configuration lists how many electrons occupy each subshell such as 1s, 2p, or 3d. Reading the notation tells you which orbitals are filled, which shell the valence electrons occupy, and where the element sits in the broad periodic-table filling pattern.
This page is designed for neutral atoms in their ground state. It starts from atomic number, which equals the number of electrons in a neutral atom, and then fills orbitals in the standard order before applying known ground-state exceptions where a more stable arrangement is observed experimentally.
Element lookup, ion charge, and what the input means
Many people search for an electron configuration calculator because they know the element symbol, not the atomic number. The calculator now accepts entries such as Fe, iron, 26, O, Cu, Ag, Au, or uranium, then resolves that input against the periodic table before it builds the configuration. Quick examples are included for common homework checks such as carbon, oxygen ion, iron, chromium, copper(I), silver, gold, and uranium.
The optional charge field changes the electron count. A positive charge models a cation by removing electrons, while a negative charge models an anion by adding electrons. For transition-metal cations, the calculator removes the outer ns electrons before the occupied (n-1)d subshell, which is the convention behind common examples such as Fe²⁺ becoming [Ar] 3d⁶.
The filling order used here
The usual filling sequence follows the Aufbau pattern: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p. Within each subshell, the orbital diagram fills one electron into each box before pairing them, which reflects Hund's rule in the simplified notation shown here.
That order is a strong first approximation, but it is not perfect for every neutral atom. Transition metals and heavier elements can shift one electron between nearby subshells to reach a lower-energy ground state, so a good calculator should not treat the naive filling sequence as universally exact.
Reading the calculator result
The full electron configuration writes every occupied subshell, while the noble-gas shorthand replaces a filled core with the nearest matching noble gas in brackets. That condensed electron configuration is useful because it makes the outer-shell and valence pattern easier to inspect without rewriting all of the inner electrons.
The shell distribution groups electrons by principal shell, and the valence-shell configuration isolates the highest occupied shell. The orbital diagram then shows how electrons are placed into individual s, p, d, or f orbitals, including unpaired electrons. Those unpaired-electron counts are often the fastest way to sanity-check Hund's rule in a classroom problem.
Worked example: iron and chromium
For iron, atomic number 26, the ground-state configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶, which is commonly written as [Ar] 4s² 3d⁶. The shell distribution is 2, 8, 14, 2, and the orbital diagram shows the 3d subshell with six electrons distributed across five d orbitals.
Chromium is a useful exception check. A simple Aufbau-only model would suggest [Ar] 4s² 3d⁴, but the experimentally observed ground state is [Ar] 4s¹ 3d⁵. If a calculator does not account for that kind of exception, it is fine for rough classroom pattern spotting but not for reliable ground-state reference.
Where this model stops
This page is for neutral atoms and ground-state configurations only. It does not calculate ionic configurations, excited states, term symbols, spin-orbit coupling, or spectroscopic notation beyond a simplified orbital-filling view.
The orbital boxes are a teaching aid, not a full quantum-mechanical wavefunction model. They are useful for pattern recognition and periodic-table reasoning, but serious spectroscopy work still depends on experimental reference data and formal atomic-structure methods.
Why ion configurations need care
Ion electron configurations are a common source of mistakes because the order used for filling neutral atoms is not always the same order used when electrons are removed. The classic example is that 4s fills before 3d in many neutral atoms, but transition-metal cations usually lose 4s electrons before 3d electrons.
This page handles those common chemistry-class conventions directly and makes the ion assumption visible in the result. It is still a simplified calculator: unusual oxidation states, ligand-field effects, excited states, and spectroscopy-grade ground states should be checked against NIST or another authoritative atomic-data reference.
Frequently asked questions
Can I enter an element symbol instead of an atomic number?
Yes. You can type an element name, symbol, or atomic number, such as Fe, iron, 26, O, oxygen, or 8. The calculator resolves the element first and then builds the electron configuration from the matching atomic number.
Why does 4s fill before 3d but appear after 3d in shorthand discussions?
The basic filling order places 4s before 3d for many neutral atoms, but once the d subshell is occupied the relative energies become more subtle. That is why shorthand and ion-formation discussions often focus on 3d occupancy and why some ground-state exceptions shift electrons between 4s and 3d.
Why do chromium and copper count as exceptions?
Those atoms gain extra stability from half-filled or filled d subshell patterns. As a result, one electron shifts from 4s into 3d, producing [Ar] 4s¹ 3d⁵ for chromium and [Ar] 4s¹ 3d¹⁰ for copper rather than the naive Aufbau-only result.
Can I use this calculator for ions?
Yes for common classroom-style ions, with caveats. Enter a positive charge for cations or a negative charge for anions. The page removes transition-metal cation electrons from the outer ns shell before the occupied (n-1)d subshell, but unusual oxidation states and spectroscopy work should still be checked against authoritative atomic-data references.
How do I find the electron configuration for Fe2+?
Enter Fe or iron, then set charge to 2. The neutral iron configuration is [Ar] 4s² 3d⁶, and Fe²⁺ removes the two 4s electrons first, giving [Ar] 3d⁶.
What is noble-gas shorthand in an electron configuration?
Noble-gas shorthand replaces the filled inner-electron core with the nearest matching noble gas in brackets. For example, iron can be written as [Ar] 4s² 3d⁶ instead of writing every filled subshell from 1s onward.
What does an unpaired electron count tell me?
The unpaired count summarizes how many orbital boxes contain one electron rather than a paired pair in the simplified diagram. It helps check Hund's rule and can hint at magnetic behavior, but it is still a teaching-level orbital model rather than a full quantum calculation.
What does the orbital diagram add beyond the configuration string?
The orbital diagram shows how electrons occupy individual orbitals inside a subshell, making Hund's rule and electron pairing easier to see. It is especially useful for understanding p, d, and f filling patterns visually.
