|Type:Noble Gas||Atomic weight:39.948|
|Density @ 293 K:0.001784 g/cm3||Atomic volume:22.4 dm3/mol at 0 °C, 101.325 kPa.|
Argon was discovered in 1894 by Lord Rayleigh and Sir William Ramsay who sought to explain why nitrogen from air appeared to be heavier than nitrogen released from compounds. They discovered that air-sourced nitrogen contained another gas that is nearly one-and-a-half times denser than nitrogen. After isolating the new gas, the first of the noble gases to be discovered, the scientists named it argon ("the inactive one") and found it made up almost one percent of air. Rayleigh said, "Argon must not be deemed rare. A large hall may easily contain a greater weight of it than a man can carry."
|State (s, l, g):gas|
|Melting point:83.85 K (-189.3 °C)||Boiling point:87.3 K (-185.8 °C)|
|Specific heat capacity:0.520 J/gK||Heat of atomization:0 kJ mol-1|
|Heat of fusion:1.188 kJ mol-1||Heat of vaporization :6.447 kJ mol-1|
|1st ionization energy:1520.5 kJ mol-1||2nd ionization energy:2665.8 kJ mol-1|
|3rd ionization energy: 3930.8 kJ mol-1||Electron affinity:kJ mol-1|
|Shells: 2,8,8||Electron configuration:[Ne] 3s23p6|
|Minimum oxidation number:0||Maximum oxidation number:0|
|Min. common oxidation no.:0||Max. common oxidation no.:0|
|Electronegativity (Pauling Scale):||Polarizability volume:1.586 Å3|
|Structure:fcc: face-centered cubic when solid||Color:Colorless|
Argon is considered to be non toxic.
Argon is a noble gas. It is colorless, odorless and extremely unreactive. It is, however, not completely inert - photolysis of hydrogen fluoride in a solid argon matrix at 7.5 kelvin yields argon fluorohydride, HArF. Argon forms no stable compounds at room temperature.
As a result of its unreactiveness, argon is used in light bulbs to protect the filament and to provide an unreactive atmosphere in the vicinity of welding.
|Reaction with air:none||Reaction with 6 M HCl:none|
|Reaction with 15 M HNO3:none||Reaction with 6 M NaOH:none|
|Atomic radius:71 pm (measured)||Ionic radius (1+ ion):pm|
|Ionic radius (2+ ion):pm||Ionic radius (3+ ion):pm|
|Ionic radius (2- ion):pm||Ionic radius (1- ion):pm|
|Thermal conductivity:1.77 x 10-2 W m-1 K-1||Electrical conductivity:0 mS cm-1|
|Abundance earth's crust: 3.5 parts per million by weight, 1.8 parts per million by moles|
|Abundance solar system:0.01 percent by weight, 3.3 parts per million by moles|
|Cost, pure:$0.5 per 100g|
|Cost, bulk:$ per 100g|
Argon is produced when 40K present naturally in the earth's crust undergoes radioactive decay to 40Ar. The argon makes its way into the atmosphere. Argon is produced commercially by fractional distillation of liquefied air with (for high purity argon) catalytic burning of left over traces of oxygen.
18 whose half-lives are known, mass numbers 30 to 47. Of these, three are stable. They are found naturally in the percentages shown: 36Ar (0.337%), 38Ar (0.063%) and 40Ar (99.600%).