Argon was the first noble gas to be discovered. Argon was suspected to be present in air by Henry Cavendish in 1785. But it was discovered in 1894 by Lord Rayleigh and Sir William Ramsay.
Name: argon
Symbol: Ar
Atomic number: 18
Atomic weight: 39.948
State: gas
Group, period, block: 18, 3, p
Color: colorless
Classification: noble gases
Electron configuration: 3s2 3p6
2,8,8
Physical properties
Density @293 K: 1.784 g/cm3
Melting point: 83.80 K, -189.35 °C, -308.83 °F
Boiling point: 87.30 K, -185.85 °C, -302.53 °F
Atomic properties
Oxidation states: 2, 1, 0
Electronegativity: no data (Pauling scale)
Ionization energies: 1st: 1520.6 kJ·mol-1
Covalent radius: 106±10 pm
Van der Waals radius: 188 pm
- Ar
Electron Configuration
Isotopes
There are three naturally occurring isotopes of argon exist, 36Ar, 38Ar and 40Ar.