Argon ( Ar )

• Atomic number: 18
• Appearance: colorless gas
• Standard atomic weight: 39.95
• Group: group 18 (noble gases)
• Period: 3
• Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶
• Element category: noble gas
• Melting point: 83.81 K
• Boiling point: 87.302 K
• Sublimation point:
Standard Temperature ( 273.15 ) and Pressure ( 1 bar = 10⁵ Pa )
• Phase at STP: gas
• Density at STP:
• Heat of fusion: 1.18 kJ/mol
• Heat of vaporization: 6.53 kJ/mol
• Molar heat capacity: 20.85 kJ/(mol·K)
• Oxidation states: 0
• Electronegativity: Pauling scale: no data
• Covalent radius: 106 pm (1×10⁻¹² m)
• Van der Waals radius: 188 pm (1×10⁻¹² m)
• Crystal structure:
• Speed of sound: 323 m/s (gas, 27 °C)
• Thermal expansion:
• Thermal conductivity: 1018 W/(m·K)