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Astronomy Chemical element

Argon

Argon (Ar) is a chemical element belonging to the category Noble gas, with atomic number 18 and standard atomic mass 39.9480 u. This sheet describes its fundamental properties, periodic position and physical characteristics.

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Astronomy · Chemical element

Argon

ELI

Identity

  • Name: Argon
  • Symbol: Ar
  • Atomic number: 18
  • Atomic mass: 39.9480 u

Position in the periodic table

  • Group: 18
  • Period: 3
  • Category: Noble gas

Physico-chemical properties

  • Standard state: Gas
  • Melting point: −189.3 °C
  • Boiling point: −185.8 °C
  • Density (gas, 0 °C, 1 atm): 0.001784 g/cm³
  • Electron configuration: [Ne] 3s² 3p⁶

Scientific description

Argon is a colorless, odourless noble gas with symbol Ar and atomic number 18. It occupies group 18 and period 3 of the periodic table and is chemically very inert under standard conditions. Its standard atomic mass is 39.9480 u, and it is the third most abundant gas in the Earth's atmosphere.