Electronic configuration calculator: enter any element, ion or compound (for example Na, Cl⁻, Mg²⁺, H₂O or Al₂O₃) to see its electronic configuration, Bohr model, valence electrons, Lewis structure and bonding instantly. Free, with no sign-up.
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What is electronic configuration?
Electronic configuration is the way electrons are arranged in the shells and orbitals of an atom. For example, sodium (11 electrons) has the electronic configuration 1s² 2s² 2p⁶ 3s¹, which gives the shell distribution 2, 8, 1. Knowing it helps you find valence electrons, valency, the ion an element forms and the type of bond it makes.
Features of this electronic configuration tool
- Electronic configuration of all 118 elements in full and short (noble gas) form, with orbital box diagrams.
- Bohr model: animated electron shells (K, L, M, N) for any atom or ion.
- Valence electrons and valency for every element, shown separately from oxidation states.
- Ion formation: see Na → Na⁺ and Cl → Cl⁻ step by step.
- Ionic and covalent bonding: NaCl, MgCl₂, CaCl₂, H₂O, CO₂, NH₃, CH₄, O₂ and N₂.
- Lewis structures, VSEPR shapes and a rotatable 3D molecule.
- Teacher mode and quiz mode for classroom use.
How to use the electronic configuration calculator
- Type an element name, symbol or atomic number (for example "sodium", "Na" or "11").
- For an ion, add its charge: Na+, Cl-, Mg2+, O2-.
- For a compound, type the formula: NaCl, H2O, Ca(OH)2, Al2(SO4)3.
- Press Visualize, then use the tabs: Bohr Shells, Orbital Configuration, Lewis Structure, Bonding, Ion Formation, Molecular Geometry and Data.
Electronic configuration of the first 20 elements
| Z | Element | Electronic configuration | Shells |
|---|---|---|---|
| 1 | Hydrogen (H) | 1s¹ | 1 |
| 2 | Helium (He) | 1s² | 2 |
| 3 | Lithium (Li) | 1s² 2s¹ | 2, 1 |
| 4 | Beryllium (Be) | 1s² 2s² | 2, 2 |
| 5 | Boron (B) | 1s² 2s² 2p¹ | 2, 3 |
| 6 | Carbon (C) | 1s² 2s² 2p² | 2, 4 |
| 7 | Nitrogen (N) | 1s² 2s² 2p³ | 2, 5 |
| 8 | Oxygen (O) | 1s² 2s² 2p⁴ | 2, 6 |
| 9 | Fluorine (F) | 1s² 2s² 2p⁵ | 2, 7 |
| 10 | Neon (Ne) | 1s² 2s² 2p⁶ | 2, 8 |
| 11 | Sodium (Na) | 1s² 2s² 2p⁶ 3s¹ | 2, 8, 1 |
| 12 | Magnesium (Mg) | 1s² 2s² 2p⁶ 3s² | 2, 8, 2 |
| 13 | Aluminium (Al) | 1s² 2s² 2p⁶ 3s² 3p¹ | 2, 8, 3 |
| 14 | Silicon (Si) | 1s² 2s² 2p⁶ 3s² 3p² | 2, 8, 4 |
| 15 | Phosphorus (P) | 1s² 2s² 2p⁶ 3s² 3p³ | 2, 8, 5 |
| 16 | Sulfur (S) | 1s² 2s² 2p⁶ 3s² 3p⁴ | 2, 8, 6 |
| 17 | Chlorine (Cl) | 1s² 2s² 2p⁶ 3s² 3p⁵ | 2, 8, 7 |
| 18 | Argon (Ar) | 1s² 2s² 2p⁶ 3s² 3p⁶ | 2, 8, 8 |
| 19 | Potassium (K) | 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ | 2, 8, 8, 1 |
| 20 | Calcium (Ca) | 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² | 2, 8, 8, 2 |
Rules for writing electronic configuration
- Aufbau principle: electrons fill the lowest-energy orbitals first (1s, 2s, 2p, 3s, 3p, 4s, 3d…).
- Pauli exclusion principle: an orbital holds at most two electrons with opposite spins.
- Hund's rule: electrons occupy orbitals of the same energy singly before pairing up.
- Exceptions: chromium is [Ar] 3d⁵ 4s¹ and copper is [Ar] 3d¹⁰ 4s¹, because half-filled and fully filled d subshells are extra stable.
Frequently asked questions about electronic configuration
What is the electronic configuration of sodium?
Sodium (Z = 11) has the electronic configuration 1s² 2s² 2p⁶ 3s¹, or [Ne] 3s¹. Its shell distribution is 2, 8, 1 and it has one valence electron.
How do you write the electronic configuration of an ion?
Write the configuration of the neutral atom, then remove electrons for a positive ion or add electrons for a negative ion. Na⁺ has 10 electrons (1s² 2s² 2p⁶), the same as neon. Cl⁻ has 18 electrons (1s² 2s² 2p⁶ 3s² 3p⁶), the same as argon.
How do you find the number of valence electrons?
For main-group elements, valence electrons are the electrons in the outermost shell. Sodium has 1, magnesium 2, carbon 4, oxygen 6 and chlorine 7. Transition metals are more complicated because d electrons can also take part in bonding.
What is the difference between valency and oxidation state?
Valency is the combining capacity of an atom, such as 2 for oxygen. An oxidation state is a signed charge assigned to an atom in a compound, such as −2 for oxygen in water. An element can have one valency but several oxidation states, as iron has +2 and +3.
Why does sodium form Na⁺ and chlorine form Cl⁻?
Sodium loses its one outer electron to reach the stable arrangement 2, 8. Chlorine gains one electron to complete its outer shell as 2, 8, 8. The oppositely charged ions attract each other and form the ionic compound NaCl.
Is NaCl a molecule?
No. In the solid state NaCl is an ionic lattice made of Na⁺ and Cl⁻ ions. It has no separate NaCl molecules.
What is a Bohr model, and is it accurate?
The Bohr model shows electrons in circular shells (K, L, M) around the nucleus. It is a simplified teaching model. Modern chemistry describes electrons as orbitals and probability clouds.
Does this tool work for all 118 elements and for ions?
Yes. It works for all 118 elements, common ions, polyatomic ions (such as SO₄²⁻ and NH₄⁺), molecules and simple ionic compounds. Elements above atomic number 103 are theoretical predictions.
Is the electronic configuration calculator free?
Yes. It is free, needs no sign-up and works on phones, tablets and computers.
Created for students and teachers of chemistry. Related tools: more free science calculators.