Argon (Ar): Electron Configuration, Properties and Uses
Argon (Ar): Electron Configuration, Properties and Uses
Electron configuration [Ne] 3s2 3p6 · group 18 · period 3 · Ar 39.948
Argon data
- Atomic number
- 18
- Relative atomic mass
- 39.948
- Group
- 18
- Period
- 3
- Block
- p
- Category
- Noble gas
- Electron configuration
- [Ne] 3s2 3p6
- Full configuration
- 1s2 2s2 2p6 3s2 3p6
- Electrons per shell
- 2, 8, 8 (K L M)
- Valence electrons
- 8
- Electronegativity (Pauling)
- no data
- First ionisation energy
- 15.76 eV
- Atomic radius (van der Waals)
- 188 pm
- State at room temperature
- Gas
- Melting point
- −189 °C
- Boiling point
- −186 °C
- Density
- 1.784 g/L (0 °C, 1 atm)
- Common oxidation states
- 0
- Discovered
- 1894
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 8
Orbital diagram (outer electrons)
About argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is a noble gas in group 18, period 3, p-block. Argon was first discovered in 1894. At room temperature argon is a gas that is heavier than air (1.784 g/L) and liquefies at −186 °C.
Argon electron configuration
The electron configuration of argon is 1s2 2s2 2p6 3s2 3p6, or in short [Ne] 3s2 3p6. Its electrons occupy 3 shells: K = 2, L = 8, M = 8. Argon has 8 valence electrons in the M shell (3s2 3p6), which is why it sits in group 18.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18)
Uses of argon
The main uses of argon include welding shielding gas, filling incandescent bulbs, inert atmospheres in glove boxes, and the plasma in ICP-OES and ICP-MS.
Safety
Argon is non-toxic and almost unreactive, but large amounts in a closed room can displace oxygen. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 18
Frequently asked questions
What is the electron configuration of argon?
The electron configuration of argon (Ar, atomic number 18) is 1s2 2s2 2p6 3s2 3p6, or [Ne] 3s2 3p6 in short. By shell: 2, 8, 8.
How many valence electrons does argon have?
Argon has 8 valence electrons.
Which group and period is argon in?
Argon is in group 18, period 3, p-block.
What is the atomic mass of argon?
The relative atomic mass of argon is 39.948. Use it to calculate molar mass with the molar mass calculator.
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