Electron Configuration Calculator
Select any element to see its ground-state orbital filling, noble-gas shorthand, shell population, and key atomic facts.
Choose an element
Elements are listed by atomic number. The calculator opens with copper as a worked example.
Workbook ready.
Occupied subshells
| Subshell | Capacity | Electrons | Filled |
|---|
How to use the electron configuration calculator
What this calculator does. It identifies the ground-state distribution of electrons among atomic subshells for a neutral atom. It also reports the element symbol, atomic number, standard atomic mass, shell population, noble-gas shorthand, and a compact valence configuration. This is a lookup-and-derivation tool for chemistry study and checking hand calculations; it does not predict excited states, ion configurations, bonding geometry, or the detailed energies of individual orbitals.
When to use it. Use it to check homework involving Aufbau filling, prepare orbital diagrams, compare neighboring elements, identify the electrons outside a noble-gas core, or verify familiar exceptions such as copper. It is also useful when translating between atomic number, full notation, shorthand notation, and shell counts.
How to calculate.
- The calculator opens with copper selected, so the first screen already shows a complete example and the Excel workbook is immediately available.
- Open the Element list and choose an atomic number and symbol. The results update live; no Calculate button is needed.
- Read Full electron configuration for the complete occupied-subshell sequence. Then compare it with Noble-gas shorthand to see which closed-shell core has been condensed.
- Use Shell population for electrons grouped by principal energy level and Valence configuration for the outer and chemically relevant subshells.
- Select Download Excel to export the current element and all displayed subshell rows to a real XLSX workbook. Select Reset to clear the demonstration; export is disabled until an element is chosen again.
Input guide. Element is the only input and is required. It accepts one of the 118 neutral elements, listed as atomic number followed by symbol; for example, “29 – Cu.” Choosing a higher atomic number generally adds electrons and may add occupied subshells, but the exact final arrangement can include stability-driven exceptions. A common mistake is to treat the simple diagonal rule as exception-free or to remove electrons from the wrong subshell when later adapting a neutral configuration to an ion.
Output guide. Full electron configuration is an exact notation for the selected neutral ground state. Element symbol and Atomic number identify the element; the atomic number also equals the electron count for a neutral atom. Atomic mass is a standard atomic-weight value in unified atomic mass units and is not the same as mass number for a particular isotope. Noble-gas shorthand replaces the preceding closed-shell core with a bracketed noble-gas symbol. Shell population totals electrons by principal shell. Valence configuration highlights the highest principal shell and, for transition or inner-transition elements, the nearby partially filled d or f subshells that are often chemically relevant. In the table, Capacity is the maximum occupancy of that subshell type, Electrons is the actual occupancy, and Filled states whether the subshell has reached capacity.
Worked example. Copper has atomic number 29, so a neutral copper atom has 29 electrons. The simple diagonal sequence would suggest 3d⁹4s² after the argon core, but the observed ground state is more stable as 3d¹⁰4s¹. Therefore the first-open result is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹, with shorthand [Ar] 3d¹⁰ 4s¹ and shell population 2, 8, 18, 1.
Learn more. The Chemistry LibreTexts explanation of electron configurations develops the Aufbau principle, Hund's rule, and shorthand notation in more detail.
How the model works
The filling engine starts with the standard energy order 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p. Each s subshell can hold 2 electrons, p holds 6, d holds 10, and f holds 14. After the base filling is complete, the calculator applies a compact set of accepted ground-state exceptions where moving one or more electrons gives the observed configuration.
The NIST periodic table is a useful authoritative reference for element identities and atomic properties. For terminology and official element naming, consult the IUPAC periodic table of the elements.
Important interpretation notes
Electron configuration notation describes occupancy, not the orientation of individual electrons. To draw boxes and arrows, apply Hund's rule within degenerate orbitals and the Pauli exclusion principle within each orbital. Also remember that transition-metal ions usually lose electrons from the highest principal shell before losing electrons from the d subshell, even though the s subshell filled earlier in the neutral atom.