Argon

General:

Name:Argon Symbol:Ar
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.
Discovered:

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."

States

State (s, l, g):gas
Melting point:83.85 K (-189.3 °C) Boiling point:87.3 K (-185.8 °C)

Energies

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

Oxidation & Electrons

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

Appearance & Characteristics

Structure:fcc: face-centered cubic when solid Color:Colorless
Hardness:mohs
Harmful effects:

Argon is considered to be non toxic.

Characteristics:

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.


Uses:

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.

It is also used in the semi-conductor industry to provide an inert atmosphere for silicon and germanium crystal growth.

Argon is used in medical lasers, in ophthalmology for example to correct eye defects such as blood vessel leakage, retinal detachment, glaucoma and macular degeneration.

Argon has low thermal conductivity and is used as the gas between the glass panes in high-efficiency double and triple glazing.

Reactions

Reaction with air:none Reaction with 6 M HCl:none
Reaction with 15 M HNO3:none Reaction with 6 M NaOH:none

Compounds

Oxide(s):none Chloride(s):none
Hydride(s):none

Radius

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

Conductivity

Thermal conductivity:1.77 x 10-2 W m-1 K-1 Electrical conductivity:0 mS cm-1

Abundance & Isotopes

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
Source:

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.

Isotopes:

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%).

Other

Other:

 

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