Quick answer
An electron configuration lists the filled subshells of an atom. Hydrogen is 1s¹, with 1 electron, 1 unpaired electron and an outermost shell n = 1. Cations lose electrons from the highest n first; anions add electrons.
Enter an element symbol or name and a charge. The calculator returns the configuration, the noble-gas shorthand and the electron counts.
Related tools: Mole Calculator: Convert between mass, moles and number of particles. Percent Yield Calculator: Percent yield of a reaction.
How to use the Electron Configuration Calculator
- Type element (symbol, name or atomic number), for example Fe, iron or 26.
- Enter charge (a whole number, between -3 and 6). It starts at 0.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Element (symbol, name or atomic number) | Text, such as Fe, iron or 26 | — |
| Charge | A whole number | ≥ -3, ≤ 6, starts at 0 |
Formula and method
Formula
ground-state subshell occupancy of the neutral atom (NIST); cations lose electrons from the highest n, then the highest l; anions add electrons in the Madelung (n + l) order
IEEE-754 double precision; shown to at most 6 decimal places.
Neutral configurations are NIST's measured ground states, so exceptions such as Cr, Cu, Pd, Pt and Au are correct. Cations remove electrons from the subshell with the highest principal quantum number first, and the highest l within it (so 4s before 3d). Anions add electrons in the order 1s 2s 2p 3s … Unpaired electrons follow Hund's rule within each partially filled subshell. Elements 1 to 108 are covered; heavier elements have no measured or NIST-tabulated ground state.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Element (symbol, name or atomic number) = H; Charge = 0.
| Result | Value |
|---|---|
| Electron configuration of H | 1s¹ |
| Condensed (noble-gas) form | 1s¹ |
| Electrons | 1 |
| Unpaired electrons | 1 |
| Outermost shell (n) | 1 |
Example 2
Inputs: Element (symbol, name or atomic number) = He; Charge = 0.
| Result | Value |
|---|---|
| Electron configuration of He | 1s² |
| Condensed (noble-gas) form | 1s² |
| Electrons | 2 |
| Unpaired electrons | 0 |
| Outermost shell (n) | 1 |
Example 3
Inputs: Element (symbol, name or atomic number) = C; Charge = 0.
| Result | Value |
|---|---|
| Electron configuration of C | 1s² 2s² 2p² |
| Condensed (noble-gas) form | [He] 2s² 2p² |
| Electrons | 6 |
| Unpaired electrons | 2 |
| Outermost shell (n) | 2 |
The first line is the headline result (electron configuration of H). Below it the electron Configuration Calculator lists condensed (noble-gas) form, electrons, unpaired electrons and outermost shell (n), which describe the same case from other angles. IEEE-754 double precision; shown to at most 6 decimal places.
How subshells fill
The order follows the Aufbau principle, roughly 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s and so on. Chromium and copper are exceptions: Cr is [Ar] 3d⁵ 4s¹ rather than 3d⁴ 4s².
Ions and scope
Ground-state configurations are from NIST for neutral atoms. For cations, electrons leave the highest n shell, then the highest l subshell. Elements 109 to 118 are not offered.
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Element (symbol, name or atomic number): left empty shows "Enter element (symbol, name or atomic number)." beside that field and no result.
- Charge: entering "2" shows "This element cannot have that charge." beside that field and no result.
Choosing between the Electron Configuration Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Mole Calculator](/science/mole/) | start from and molar mass | Amount |
| [Percent Yield Calculator](/science/percent-yield/) | actual yield and theoretical yield | Percent yield |
| [Dilution Calculator](/science/dilution-ratio/) | solve for | Final volume V₂ |
| [Molarity Calculator](/science/molarity-calculator/) | solute mass, molar mass and solution volume | Molarity |
| [Average Atomic Mass Calculator](/science/average-atomic-mass/) | isotope masses and abundances | Average atomic mass |
Background: chemistry calculations
Most basic chemistry calculations chain three relations: moles n = mass ÷ molar mass, molarity M = n ÷ volume in litres, and dilution C₁V₁ = C₂V₂. Keep units consistent: grams with g/mol, litres with mol/L.
Molar masses come from standard atomic weights, which differ slightly between tables and with the isotopic make-up of a real sample.
Assumptions and limitations
- Elements 109 to 118 are not offered
- Lanthanide and actinide cations follow the same removal rule and can differ from spectroscopic ground states in a few cases
- Only monatomic species; molecules are not handled
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for element (symbol, name or atomic number) and charge to confirm this.
Frequently asked questions
What is the configuration of oxygen?
Oxygen (8 electrons) is 1s² 2s² 2p⁴, with two unpaired electrons in the 2p subshell.
What is noble-gas shorthand?
Using the previous noble gas in brackets.
What are unpaired electrons?
Electrons alone in an orbital.
What does the Electron Configuration Calculator calculate?
Ground-state electron configuration of an element or monatomic ion, with noble-gas shorthand and unpaired electrons. It returns Electron configuration of H, Condensed (noble-gas) form, Electrons, Unpaired electrons and Outermost shell (n).
What formula does the Electron Configuration Calculator use?
ground-state subshell occupancy of the neutral atom (NIST); cations lose electrons from the highest n, then the highest l; anions add electrons in the Madelung (n + l) order. Neutral configurations are NIST's measured ground states, so exceptions such as Cr, Cu, Pd, Pt and Au are correct.
What do I need to enter in the electron Configuration Calculator?
You enter Element (symbol, name or atomic number) and Charge.
How is the result rounded or limited?
IEEE-754 double precision; shown to at most 6 decimal places. Elements 109 to 118 are not offered.
What are the limits of this calculator?
Elements 109 to 118 are not offered. Lanthanide and actinide cations follow the same removal rule and can differ from spectroscopic ground states in a few cases. Only monatomic species; molecules are not handled.
What is an example of a electron Configuration result?
With element (symbol, name or atomic number) H and charge 0, the electron configuration of H is 1s¹.
Where does the method come from?
The method follows: NIST Atomic Spectra Database, Ground States and Ionization Energies (public domain), https://physics.nist.gov/PhysRefData/ASD/ionEnergy.html; Madelung (n + l) filling rule; cation convention as in standard general-chemistry texts.
Related calculators
- Mole Calculator — Convert between mass, moles and number of particles.
- Percent Yield Calculator — Percent yield of a reaction.
- Molarity Calculator — Concentration of a solution from solute mass, molar mass and volume.
- Average Atomic Mass Calculator — Weighted average of isotope masses.
- Partial Pressure Calculator — Partial pressure of a gas in a mixture (Dalton's law).
- Stoichiometry Calculator — Mass of a product (or reactant) from the mass of another species in a balanced equation.
- Molality Calculator — Molality of a solution.
Sources
- NIST Atomic Spectra Database, Ground States and Ionization Energies (public domain), https://physics.nist.gov/PhysRefData/ASD/ionEnergy.html
- Madelung (n + l) filling rule; cation convention as in standard general-chemistry texts
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.