Argon (Ar)
Argon (Ar) is element 18 of the periodic table, a noble gas in period 3 and group 18. Its standard atomic weight is 39.95, so one mole of argon atoms has a mass of 39.95 g. At room temperature it is a gas; it melts at -189.35 °C and boils at -185.85 °C.
| Atomic number | 18 |
|---|---|
| Symbol | Ar |
| Standard atomic weight | 39.95 |
| Molar mass | 39.95 g/mol |
| Category | Noble gas |
| Group | 18 |
| Period | 3 |
| Block | p-block |
| Electron configuration | [Ne] 3s2 3p6 |
| Oxidation states | 0 |
| Electronegativity (Pauling) | — |
| Atomic radius (van der Waals) | 188 pm |
| First ionisation energy | 15.76 eV (1520.6 kJ/mol) |
| Electron affinity | — |
| State at room temperature | Gas |
| Melting point | 83.8 K (-189.35 °C) |
| Boiling point | 87.3 K (-185.85 °C) |
| Density | 1.7837 g/L |
| Discovered | 1894 |
Group 18
Calculate with Argon
Atomic weight: IUPAC CIAAW standard atomic weight. Other properties: PubChem (U.S. National Library of Medicine, public domain). Values such as melting point and radius depend on how they were measured; check a data book for precise work.