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.
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
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.
How it works
- The Aufbau principle fills subshells from lowest to highest energy: 1s → 2s → 2p → 3s → 3p.
- Argon's 18 electrons completely fill four 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.