Argon is the third most common gas with 0.93% of the Earth’s atmosphere. Almost all argon is radiogenic argon-40, derived from the decay of potassium-40 in the Earth’s crust.

1894 by Sir William Ramsay and Lord Rayleigh, London, England.

DISCOVERY

Ancient Greek, ἀργόν (argón), neuter of ἀργός (argós, 'idle, lazy').

ETYMOLOGY

Argon

Element

Ar

Symbol

18

18 Atomic Number

Atomic Number

Noble Gas

Classification

7440-37-1

CAS Number

Colourless

Elemental Colour

1.000'281

Refractive Index

-

Poisson Ratio

22.392 cm³

Molar Volume

-

Brinell Hardness

-

Mohs Hardness

-

Vickers Hardness

319 m/s, Mach 0.930'0

319 m/s

Speed of Sound

-

Bulk Modulus

-

Shear Modulus

-

Young Modulus

Allotropes

83.85 K, -189.30 °C

-189.30 °C

Melting Point

87.35 K, -185.80 °C

-185.80 °C

Boiling Point

-

Automatic Ignition

-

Flashpoint

150.87 K, -122.28 °C

-122.28 °C

Critical Temperature

4.90M Pa, 48 Atm

48 Atm

Critical Pressure

0.017'720 W/(m K)

Thermal Conductivity

-

Thermal Expansion

520.33 J/(kg K)

Specific Heat

1.180 kJ/mol

Heat Fusion

6.500 kJ/mol

Heat Vaporisation

-

Heat Combustion

-

Curie Point

-

Neel Point

5/3

Adiabatic Index

Gas

Phase

-

Electrical Type

-

Conductivity

-

Resistivity

-

Superconducting Point

Diamagnetic

Magnetic Type

-0.000'000'006'0

Mass Susceptibility

-0.000'000'000'240'00

Molar Susceptibility

-0.000'000'010'70

Volume Susceptibility

Material Composition

0.02 %

Universe

-

Meteorites

0.007 %

Sun

0.000'15 %

Earth Crust

0.000'045 %

Oceans

-

Humans

39.947'676'7

Atomic Weight

71 pm

Atomic Radius

96 pm

Covalent Radius Single Bond

107 pm

Covalent Radius Double Bond

96 pm

Covalent Radius Triple Bond

188 pm

Van der Waals Radius

[Ne]3s²3p⁶

Electron Configuration

Cubic, Face-centred

Crystal Structure

-

Density as Solid

-

Density as Liquid

1.784'00 g/cm³

Density as Gas

Fm_3m

Space Group Name

225

225 Space Group Number

Space Group Number

π/2, π/2 & π/2

Lattice Angles

525.6, 525.6 & 525.6 pm

Lattice Constants

0

0 Valence

Valence

-

Electronegativity

-96.49 kJ/mol

Electron Affinity

Ionisation Energy

Stable

Half Life

Stable

Lifetime

3p⁶ = 3, 1, +1, -1/2

Quantum Numbers

0.683'00 b σ_s

Neutron Cross Section

0.675'00 b σ_a

Neutron Mass Absorption

Stable Isotopes

Unstable Isotopes

Isotopes Overview

Isotope	Stability	Symbol	Type	Protons		Neutrons		Spin	Parity	Mass		Abundance		Mass Measure	Mass Excess		Binding Energy		Dipole Moment		Quadrupole Moment	Halflife in Years		Halflife in Seconds		A01 Decay Probability		A01 Decay Mode	A01 Decay Energy		A01 Decay Daughter	A01 Decay Link	A02 Decay Probability		A02 Decay Mode	A02 Decay Energy		A02 Decay Daughter	A02 Decay Link	A03 Decay Probability		A03 Decay Mode	A03 Decay Energy		A03 Decay Daughter	A03 Decay Link	A04 Decay Probability		A04 Decay Mode	A04 Decay Energy		A04 Decay Daughter	A04 Decay Link	A05 Decay Probability		A05 Decay Mode	A05 Decay Energy		A05 Decay Daughter	A05 Decay Link	A06 Decay Probability		A06 Decay Mode	A06 Decay Energy		A06 Decay Daughter	A06 Decay Link	Y01 Decay Product Yield		Y01 Decay Product Nuclide	Y02 Decay Product Yield		Y02 Decay Product Nuclide	Y03 Decay Product Yield		Y03 Decay Product Nuclide	Y04 Decay Product Yield		Y04 Decay Product Nuclide	Y05 Decay Product Yield		Y05 Decay Product Nuclide	Y06 Decay Product Yield		Y06 Decay Product Nuclide	Y07 Decay Product Yield		Y07 Decay Product Nuclide	Y08 Decay Product Yield		Y08 Decay Product Nuclide	Y09 Decay Product Yield		Y09 Decay Product Nuclide	Y10 Decay Product Yield		Y10 Decay Product Nuclide	Y11 Decay Product Yield		Y11 Decay Product Nuclide	Y12 Decay Product Yield		Y12 Decay Product Nuclide
Isotope_018_ar_30_u	Unstable	³⁰Ar	Boson	18	p	12	n	0	1	30.021'560'000'0	u	~ 0	%	~ 0	20.083'000'000'0	MeV	6.932'000'000'0	MeV	-		-	6.34E-16	year	20.000	nano-seconds ( x⁻⁹ )	?	%	2p	1,432.000	keV	²⁸S	³⁰Ar > [ ? % , 2p , 1,432.0 keV ] > ²⁸S																																				?	%	²⁸Si	?	%	²⁴Mg	?	%	²⁷Al
Isotope_018_ar_31_u	Unstable	³¹Ar	Boson	18	p	13	n	5/2	1	31.012'123'000'0	u	~ 0	%	~ 0	11.293'000'000'0	MeV	7.253'000'000'0	MeV	-		-	4.56E-10	year	14.400	milli-seconds ( x⁻³ )	63.000'000	%	β+p	?	keV	³⁰S	³¹Ar > [ 63 % , β+p , ? keV ] > ³⁰S	28.000'000	%	β+	17,338.000	keV	³¹Cl	³¹Ar > [ 28 % , β+ , 17,338.0 keV ] > ³¹Cl	0.072'000	%	β+2p	?	keV	²⁹P	³¹Ar > [ 0.072 % , β+2p , ? keV ] > ²⁹P	0.014'000	%	β+3p	?	keV	²⁸Si	³¹Ar > [ 0.014 % , β+3p , ? keV ] > ²⁸Si	0.003'800	%	β+pα	?	keV	²⁶Si	³¹Ar > [ 0.0038 % , β+pα , ? keV ] > ²⁶Si	0.030'000	%	β+α	?	keV	²⁶P	³¹Ar > [ 0.03 % , β+α , ? keV ] > ²⁶P	63.196'000	%	³⁰Si	27.720'000	%	³¹P	7.200'000	%	²⁹Si	1.400'000	%	²⁸Si	0.380'021	%	²⁶Mg	0.000'300	%	²⁷Mg	0.000'300	%	²⁷Mg	0.000'300	%	²⁷Mg	0.000'300	%	²⁷Mg	0.000'300	%	²⁷Mg	0.000'300	%	²⁷Mg	0.000'300	%	²⁷Mg
Isotope_018_ar_32_u	Unstable	³²Ar	Boson	18	p	14	n	0	1	31.997'637'984'0	u	~ 0	%	~ 0	-2.200'204'000'0	MeV	7.700'003'000'0	MeV	-		-	3.11E-9	year	98.000	milli-seconds ( x⁻³ )	57.000'000	%	β+	10,107.370	keV	³²Cl	³²Ar > [ 57 % , β+ , 10,107.37 keV ] > ³²Cl	43.000'000	%	β+p	?	keV	³¹S	³²Ar > [ 43 % , β+p , ? keV ] > ³¹S																													57.000'000	%	³²S	43.014'820	%	³¹P	0.030'780	%	²⁸Si
Isotope_018_ar_33_u	Unstable	³³Ar	Fermion	18	p	15	n	1/2	1	32.989'925'709'0	u	~ 0	%	~ 0	-9.384'141'000'0	MeV	7.928'950'000'0	MeV	-		-	5.48E-9	year	173.000	milli-seconds ( x⁻³ )	61.000'000	%	β+	10,597.091	keV	³³Cl	³³Ar > [ 61 % , β+ , 10,597.091 keV ] > ³³Cl	38.700'000	%	β+p	?	keV	³²S	³³Ar > [ 38.7 % , β+p , ? keV ] > ³²S																													61.000'000	%	³³S	38.100'000	%	³²S
Isotope_018_ar_34_u	Unstable	³⁴Ar	Boson	18	p	16	n	0	1	33.980'271'244'0	u	~ 0	%	~ 0	-18.377'217'000'0	MeV	8.197'640'000'0	MeV	-		-	2.68E-8	year	845.000	milli-seconds ( x⁻³ )	100.000'000	%	β+	5,040.359	keV	³⁴Cl	³⁴Ar > [ 100 % , β+ , 5,040.359 keV ] > ³⁴Cl																																				100.000'000	%	³⁴S
Isotope_018_ar_35_u	Unstable	³⁵Ar	Fermion	18	p	17	n	3/2	1	34.975'257'585'0	u	~ 0	%	~ 0	-23.047'411'000'0	MeV	8.327'465'000'0	MeV	0.633'000'000'0	nm	-	5.62E-8	year	1.775	seconds ( x⁰ )	100.000'000	%	β+	4,943.929	keV	³⁵Cl	³⁵Ar > [ 100 % , β+ , 4,943.929 keV ] > ³⁵Cl																																				100.000'000	%	³⁵Cl
Isotope_018_ar_36_s	Stable	³⁶Ar	Boson	18	p	18	n	0	1	35.967'545'105'0	u	0.336'500	%	0.121'030'789'3	-30.231'540'000'0	MeV	8.519'909'000'0	MeV	-		-	-
Isotope_018_ar_37_u	Unstable	³⁷Ar	Fermion	18	p	19	n	3/2	1	36.966'776'320'0	u	~ 0	%	~ 0	-30.947'659'000'0	MeV	8.527'139'000'0	MeV	1.145'000'000'0	nm	-	9.59E-2	year	3.027	mega-seconds ( x⁶ )	100.000'000	%	ϵ	813.873	keV	³⁷Cl	³⁷Ar > [ 100 % , ϵ , 813.873 keV ] > ³⁷Cl																																				100.000'000	%	³⁷Cl
Isotope_018_ar_38_s	Stable	³⁸Ar	Boson	18	p	20	n	0	1	37.962'732'394'0	u	0.063'200	%	0.023'992'446'9	-34.714'551'000'0	MeV	8.614'273'000'0	MeV	-		-	-
Isotope_018_ar_39_u	Unstable	³⁹Ar	Fermion	18	p	21	n	7/2	-1	38.964'313'231'0	u	~ 0	%	~ 0	-33.242'011'000'0	MeV	8.562'593'000'0	MeV	-1.300'000'000'0	nm	-	2.69E+2	years	8.495	giga-seconds ( x⁹ )	100.000'000	%	β-	565.000	keV	³⁹K	³⁹Ar > [ 100 % , β- , 565.0 keV ] > ³⁹K																																				100.000'000	%	³⁹Cl
Isotope_018_ar_40_s	Stable	⁴⁰Ar	Boson	18	p	22	n	0	1	39.962'383'122'5	u	99.600'300	%	39.802'653'477'2	-35.039'896'020'0	MeV	8.595'259'000'0	MeV	-		-	-
Isotope_018_ar_41_u	Unstable	⁴¹Ar	Fermion	18	p	23	n	7/2	-1	40.964'500'611'0	u	~ 0	%	~ 0	-33.067'467'000'0	MeV	8.534'371'000'0	MeV	-		-	2.08E-4	year	6.577	kilo-seconds ( x³ )	100.000'000	%	β-	2,491.606	keV	⁴¹K	⁴¹Ar > [ 100 % , β- , 2,491.606 keV ] > ⁴¹K																																				100.000'000	%	⁴¹Cl
Isotope_018_ar_42_u	Unstable	⁴²Ar	Boson	18	p	24	n	0	1	41.963'045'736'0	u	~ 0	%	~ 0	-34.422'675'000'0	MeV	8.555'613'000'0	MeV	-		-	3.30E+1	years	1.041	giga-seconds ( x⁹ )	100.000'000	%	β-	598.880	keV	⁴²K	⁴²Ar > [ 100 % , β- , 598.88 keV ] > ⁴²K																																				100.000'000	%	⁴²Ca
Isotope_018_ar_43_u	Unstable	⁴³Ar	Fermion	18	p	25	n	5/2	1	42.965'636'056'0	u	~ 0	%	~ 0	-32.009'808'000'0	MeV	8.488'237'000'0	MeV	-		-	1.02E-5	year	322.020	seconds ( x⁰ )	100.000'000	%	β-	4,583.400	keV	⁴³K	⁴³Ar > [ 100 % , β- , 4,583.4 keV ] > ⁴³K																																				100.000'000	%	⁴³Ca
Isotope_018_ar_44_u	Unstable	⁴⁴Ar	Boson	18	p	26	n	0	1	43.964'924'033'0	u	~ 0	%	~ 0	-32.673'053'000'0	MeV	8.493'836'000'0	MeV	-		-	2.26E-5	year	712.200	seconds ( x⁰ )	100.000'000	%	β-	3,136.600	keV	⁴⁴K	⁴⁴Ar > [ 100 % , β- , 3,136.6 keV ] > ⁴⁴K																																				100.000'000	%	⁴⁴Ca
Isotope_018_ar_45_u	Unstable	⁴⁵Ar	Fermion	18	p	27	n	?	-1	44.968'039'956'0	u	~ 0	%	~ 0	-29.770'589'000'0	MeV	8.419'947'000'0	MeV	-		-	6.81E-7	year	21.480	seconds ( x⁰ )	100.000'000	%	β-	6,837.600	keV	⁴⁵K	⁴⁵Ar > [ 100 % , β- , 6,837.6 keV ] > ⁴⁵K																																				100.000'000	%	⁴⁵Sc
Isotope_018_ar_46_u	Unstable	⁴⁶Ar	Boson	18	p	28	n	0	1	45.968'094'129'0	u	~ 0	%	~ 0	-29.720'127'000'0	MeV	8.411'271'000'0	MeV	-		-	2.66E-7	year	8.400	seconds ( x⁰ )	100.000'000	%	β-	5,698.200	keV	⁴⁶K	⁴⁶Ar > [ 100 % , β- , 5,698.2 keV ] > ⁴⁶K																																				?	%	⁴⁶Ti
Isotope_018_ar_47_u	Unstable	⁴⁷Ar	Fermion	18	p	29	n	3/2	-1	46.972'186'792'0	u	~ 0	%	~ 0	-25.907'836'000'0	MeV	8.322'926'000'0	MeV	-		-	1.84E-8	year	580.000	milli-seconds ( x⁻³ )	99.000'000	%	β-	9,788.000	keV	⁴⁷K	⁴⁷Ar > [ 99 % , β- , 9,788.0 keV ] > ⁴⁷K	1.000'000	%	β-n	1,439.000	keV	⁴⁶K	⁴⁷Ar > [ 1 % , β-n , 1,439.0 keV ] > ⁴⁶K																													99.000'000	%	⁴⁷Ti	?	%	⁴⁶Ti
Isotope_018_ar_48_u	Unstable	⁴⁸Ar	Boson	18	p	30	n	0	1	47.974'540'000'0	u	~ 0	%	~ 0	-23.716'000'000'0	MeV	8.272'000'000'0	MeV	-		-	1.58E-8	year	500.000	milli-seconds ( x⁻³ )	?	%	β-	8,408.000	keV	⁴⁸K	⁴⁸Ar > [ ? % , β- , 8,408.0 keV ] > ⁴⁸K																																				?	%	⁴⁸Ti	?	%	⁴⁷Ti
Isotope_018_ar_49_u	Unstable	⁴⁹Ar	Fermion	18	p	31	n	3/2	-1	48.980'520'000'0	u	~ 0	%	~ 0	-18.146'000'000'0	MeV	8.154'000'000'0	MeV	-		-	5.39E-9	year	170.000	milli-seconds ( x⁻³ )	65.000'000	%	β-n	5,907.000	keV	⁴⁸K	⁴⁹Ar > [ 65 % , β-n , 5,907.0 keV ] > ⁴⁸K	35.000'000	%	β-	12,174.000	keV	⁴⁹K	⁴⁹Ar > [ 35 % , β- , 12,174.0 keV ] > ⁴⁹K																													0.741'000	%	⁴⁷Ti	?	%	⁴⁸Ti
Isotope_018_ar_50_u	Unstable	⁵⁰Ar	Boson	18	p	32	n	0	1	49.984'430'000'0	u	~ 0	%	~ 0	-14.503'000'000'0	MeV	8.080'000'000'0	MeV	-		-	2.69E-9	year	85.000	milli-seconds ( x⁻³ )	65.000'000	%	β-	10,849.000	keV	⁵⁰K	⁵⁰Ar > [ 65 % , β- , 10,849.0 keV ] > ⁵⁰K	35.000'000	%	β-n	7,745.000	keV	⁴⁹K	⁵⁰Ar > [ 35 % , β-n , 7,745.0 keV ] > ⁴⁹K																													46.150'000	%	⁵⁰Ti	18.850'000	%	⁴⁹Ti	?	%	⁴⁸Ti
Isotope_018_ar_51_u	Unstable	⁵¹Ar	Fermion	18	p	33	n	3/2	-1	50.991'630'000'0	u	~ 0	%	~ 0	-7.797'000'000'0	MeV	7.948'000'000'0	MeV	-		-	1.90E-9	year	60.000	milli-seconds ( x⁻³ )	?	%	β-	14,205.000	keV	⁵¹K	⁵¹Ar > [ ? % , β- , 14,205.0 keV ] > ⁵¹K																																				?	%	⁵¹V	?	%	⁵⁰Ti
Isotope_018_ar_52_u	Unstable	⁵²Ar	Boson	18	p	34	n	0	1	51.996'780'000'0	u	~ 0	%	~ 0	-2.999'000'000'0	MeV	7.858'000'000'0	MeV	-		-	3.17E-10	year	10.000	milli-seconds ( x⁻³ )	?	%	β-	13,200.000	keV	⁵²K	⁵²Ar > [ ? % , β- , 13,200.0 keV ] > ⁵²K																																				?	%	⁵¹V	?	%	⁵⁰Ti
Isotope_018_ar_53_u	Unstable	⁵³Ar	Fermion	18	p	35	n	5/2	-1	53.004'940'000'0	u	~ 0	%	~ 0	4.602'000'000'0	MeV	7.719'000'000'0	MeV	-		-	9.51E-11	year	3.000	milli-seconds ( x⁻³ )	?	%	β-	16,600.000	keV	⁵³K	⁵³Ar > [ ? % , β- , 16,600.0 keV ] > ⁵³K	?	%	β-n	12,730.000	keV	⁵²K	⁵³Ar > [ ? % , β-n , 12,730.0 keV ] > ⁵²K																													?	%	⁵¹V	?	%	⁵⁰Ti	?	%	⁵²Cr

18 – Argon, Ar

18 – Argon, Ar

18 – Argon, Ar

18 – Argon, Ar

18 – Argon, Ar

Spectrograph

Elemental Tile

Argon Ice

Spectrograph

Elemental Tile

Argon Ice

Spectrograph

Elemental Tile

Argon Ice

Spectrograph

Elemental Tile

Argon Ice

Spectrograph

Elemental Tile

Argon Ice