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| Appearance |
colorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field
Vial containing a violet glowing gas
Spectral lines of argon |
| General properties |
| Name, symbol, number |
argon, Ar, 18 |
| Pronunciation |
/ˈɑrɡɒn/ |
| Element category |
noble gases |
| Group, period, block |
18, 3, p |
| Standard atomic weight |
39.948(1) g/mol |
| Electron configuration |
[Ne] 3s2 3p6 |
| Electrons per shell |
2, 8, 8 (Image) |
| Physical properties |
| Phase |
gas |
| Density |
(0 °C, 101.325 kPa)
1.784 g/L |
| Liquid density at b.p. |
1.40 g/cm3 |
| Melting point |
83.80 K, −189.35 °C, −308.83 °F |
| Boiling point |
87.30 K, −185.85 °C, −302.53 °F |
| Triple point |
83.8058 K (-189°C), 69 kPa |
| Critical point |
150.87 K, 4.898 MPa |
| Heat of fusion |
1.18 kJ/mol |
| Heat of vaporization |
6.43 kJ/mol |
| Specific heat capacity |
(25 °C) 5R/2 = 20.786 J/(mol·K) |
| Vapor pressure |
| P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
| at T (K) |
|
47 |
53 |
61 |
71 |
87 |
|
| Atomic properties |
| Oxidation states |
0 |
| Electronegativity |
no data (Pauling scale) |
Ionization energies
|
1st: 1520.6 kJ/mol |
| 2nd: 2665.8 kJ/mol |
| 3rd: 3931 kJ/mol |
| Covalent radius |
106±10 pm |
| Van der Waals radius |
188 pm |
| Miscellanea |
| Crystal structure |
face-centered cubic |
| Magnetic ordering |
diamagnetic[1] |
| Thermal conductivity |
(300 K) 17.72x10-3 W/(m·K) |
| Speed of sound |
(gas, 27 °C) 323 m/s |
| CAS registry number |
7440–37–1 |
| Most stable isotopes |
| Main article: Isotopes of argon |
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Argon is a chemical element. The symbol for argon is Ar, and its atomic number (or proton number) is 18. It is a noble gas and no electrons or protons can be lost or gained from this atom.
Argon atoms are found in air. About 1% of the Earth's atmosphere (the air around us) is argon.
