Argon

Koushik 26/06/2026 19:58:08 Updated 26/06/2026 19:58:08

Property	Value
Atomic Number	18
Element	Argon
Symbol	Ar
Atomic Mass	39.948 u
Number of Neutrons	22 (most common isotope, Argon-40)
Number of Protons	18
Number of Electrons	18
Period	3
Group	18
Phase	Gas
Radioactive	No
Natural	Yes
Metal	No
Nonmetal	Yes
Metalloid	No
Type	Noble Gas
Atomic Radius	71 pm
Electronegativity	Not defined
First Ionization Energy	15.760 eV
Density	0.001784 g/cm³
Melting Point	−189.34 °C
Boiling Point	−185.85 °C
Number of Isotopes	3 (Argon-36, Argon-38, Argon-40)
Discoverer	Lord Rayleigh, William Ramsay
Year	1894
Specific Heat	0.520 J/g·K
Number of Shells	3
Number of Valence Electrons	8