Argon Electron Configuration
Interactive reference for argon's electron configuration (1s² 2s² 2p⁶ 3s² 3p⁶), orbital box diagram, quantum numbers, and its role as a noble-gas core for elements Z=19 and beyond.
Use the Argon Electron Configuration
Argon — Electron Configuration
Atomic number 18 · Noble gas · Period 3, Group 18 · p-block
Subshell Breakdown
| Subshell | Type | Electrons | Max Capacity | Notation |
|---|---|---|---|---|
| 1s | s orbital, shell n=1 | 2 | 2 | 1s² |
| 2s | s orbital, shell n=2 | 2 | 2 | 2s² |
| 2p | p orbitals, shell n=2 | 6 | 6 | 2p⁶ |
| 3s | s orbital, shell n=3 | 2 | 2 | 3s² |
| 3p | p orbitals, shell n=3 | 6 | 6 | 3p⁶ |
| Total | 18 | |||
Full Configuration
1s² 2s² 2p⁶ 3s² 3p⁶
All subshells written explicitly.
Noble-Gas Shorthand
[Ne] 3s² 3p⁶
[Ne] = 1s² 2s² 2p⁶ (neon's filled core).
Used as Core ([Ar])
[Ar] = 1s²…3p⁶
Shorthand for K, Ca, and all transition metals.
Shell Fill Summary
Shell 3 can hold up to 18 electrons (3s + 3p + 3d). Argon fills 8 of those 18 slots — the 3d subshell is empty, which is why the next electrons (in potassium) jump to 4s rather than 3d.
Elements That Use [Ar] as Their Core
| Element | Z | Configuration |
|---|---|---|
| Potassium (K) | 19 | [Ar] 4s¹ |
| Calcium (Ca) | 20 | [Ar] 4s² |
| Scandium (Sc) | 21 | [Ar] 3d¹ 4s² |
| Iron (Fe) | 26 | [Ar] 3d⁶ 4s² |
| Copper (Cu) | 29 | [Ar] 3d¹⁰ 4s¹ |
| Zinc (Zn) | 30 | [Ar] 3d¹⁰ 4s² |
| Krypton (Kr) | 36 | [Ar] 3d¹⁰ 4s² 4p⁶ |
Summary
Argon (Ar) has atomic number 18 and the ground-state electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶. All 18 electrons are paired across five filled subshells, giving argon its exceptional chemical inertness. This tool displays its full orbital box diagram, subshell breakdown, quantum numbers for every electron, and explains why [Ar] is used as a shorthand core in the configurations of potassium, calcium, and the transition metals.
How it works
- The Aufbau principle fills subshells from lowest to highest energy: 1s → 2s → 2p → 3s → 3p.
- Argon's 18 electrons completely fill five subshells across three principal shells.
- The 3p subshell, holding 6 electrons across three orbitals, is the outermost and closes argon's valence shell.
- With no unpaired electrons and a full outer shell, argon has zero chemical valence under normal conditions.
- In noble-gas notation, [Ar] replaces the 1s² 2s² 2p⁶ 3s² 3p⁶ core for all elements with Z ≥ 19.
- Use the tabs below to explore the configuration table, orbital diagram, and element properties.
Use cases
- Quick reference for chemistry homework or exam questions on noble-gas configurations.
- Understand why argon forms no bonds and why its ionization energy is high.
- Use [Ar] shorthand correctly when writing configurations for potassium through krypton.
- Visualize the fully paired 3p subshell that closes Period 3.
- Compare argon to neon ([Ne]) and krypton as the three classic noble-gas cores.
- Teaching aid for Aufbau principle, Hund's rule, and Pauli exclusion principle.
- Verify quantum numbers for all 18 electrons in argon.