[General | States | Energies | Oxidation & Electrons]
[Appearance & Characteristics | Reactions | Other Forms]
[Radius | Conductivity
| Abundance | History]
| Name |
Argon |
Symbol |
Ar |
| Atomic number |
18 |
Atomic weight |
39.948 |
| Density @ 293 K |
0.0017824 g/cm3 |
Atomic volume |
28.5 cm3/mol |
| Group |
Noble Gas |
Discovered |
1894 |
| State (s, l, g) |
g |
| Melting point |
84 K |
Boiling point |
87.3 K |
| Heat of fusion |
1.188 kJ/mol |
Heat of vaporization |
6.447 kJ/mol |
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| 1st ionization energy |
1520.5 kJ/mole |
Electronegativity |
|
| 2nd ionization energy |
2665.8 kJ/mole |
Electron affinity |
kJ/mole |
| 3rd ionization energy |
3930.8 kJ/mole |
Specific heat |
0.520 J/gK |
| Heat atomization |
0 kJ/mole atoms |
| Shells |
2,8,8 |
Electron configuration |
[Ne] 3s2 3p6 |
| Minimum oxidation number |
0 |
Maximum oxidation number |
0 |
| Minimum common oxidation no. |
0 |
Maximum common oxidation number |
0 |
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| Structure |
fcc: face-centered cubic |
Color |
colorless |
| Uses |
lasers, light bulbs |
Toxicity |
no |
| Hardness |
mohs |
Characteristics |
Inert |
| Reaction with air |
none |
Reaction with 6M HCl |
none |
| Reaction with 6M HCl |
none |
Reaction with 15M HNO3 |
none |
| Reaction with 6M NaOH |
none |
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| Number of isotopes |
3 |
Hydride(s) |
none |
| Oxide(s) |
none |
Chloride(s) |
none |
| Ionic radius (2- ion) |
pm |
Ionic radius (1- ion) |
pm |
| Atomic radius |
98 pm |
Ionic radius (1+ ion) |
pm |
| Ionic radius (2+ ion) |
pm |
Ionic radius (3+ ion) |
pm |
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| Thermal conductivity |
0.02 J/m-sec-deg |
Electrical conductivity |
0 1/mohm-cm |
| Polarizability |
1.586 A^3 |
| source |
Air |
rel. abund. solar system |
5.004 log |
| abundance earth's crust |
0.5 log |
cost, pure |
0.5 $/100g |
| cost, bulk |
$/100g |
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History:
(Gr. argos,
inactive) Its presence in air was suspected by
Cavendish in 1785, discovered by Lord Rayleigh
and Sir William Ramsay in 1894. The gas is
prepared by fractionation of liquid air, the
atmosphere containing 0.94% argon. The atmosphere
of Mars contains 1.6% of 40Ar and 5 p.p.m. of
36Ar. Argon is two and one half times as soluable
in water as nitrogen, having about bhe same
solubility as oxygen. It is used in electric
light bulbs and in fluorescent tubes at a
pressure of about 400 Pa. and in filling photo
tubes, glow tubes, etc. Argon is also used as an
inert gas shield for arc welding and cutting, as
blanket for the production of titanium and other
reactive elements, and as a protective atmosphere
for growing silicon and germanium crystals. Argon
is colorless and odorless, both as a gas and
liquid. Argon is considered to be a very inert
gas and is not known to form true chemical
compounds, as do kypton, xenon, and radon.
Naturally occurring argon is a mixture of three
isotopes. Twelve other radioactive isotopes are
known to exist.
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