Argon

Argon (Ar)

Argon is the 18th element in the periodic table and has a symbol of Ar and atomic number of 18. It has an atomic weight of 39.948 and a mass number of 40. Argon has eighteen protons and twenty-two neutrons in its nucleus, and eighteen electrons in three shells. It is located in group eighteen, period three and block p of the periodic table. Monatomic noble gas. Makes up 0.93% of the air. Colourless, odorless. Is inert and has no true compounds. Lord Rayleigh and Sir william Ramsey identified argon in 1894.
Atomic Number18
Atomic Weight39.948
Mass Number40
Group18
Period3
Blockp
Protons18 p+
Neutrons22 n0
Electrons18 e-
Animated Bohr Model of Ar (Argon)

Physical Properties

Atomic Radius
71 pm
Molar Volume
Covalent Radius
96 pm
Metallic Radius
Ionic Radius
Crystal Radius
Van der Waals Radius
188 pm
Density
0.001633 g/cm³
Atomic Radii of the Elements: Argon0102030405060708090100110120130140150160170180190pmAtomic RadiusCovalent RadiusMetallic RadiusVan der Waals Radius

Chemical Properties

Energy
Proton Affinity
369.2 kJ/mol
Electron Affinity
Ionization Energy
15.7596112 eV/particle
Ionization Energies of Ar (Argon)
Heat of Vaporization
6.52 kJ/mol
Heat of Fusion
Heat of Formation
Electrons
Electron Shells2, 8, 8
Bohr Model: Ar (Argon)
Valence Electrons8
Lewis Structure: Ar (Argon)
Electron Configuration[Ne] 3s2 3p6
1s2 2s2 2p6 3s2 3p6
Enhanced Bohr Model of Ar (Argon)
Orbital Diagram of Ar (Argon)
Oxidation States0
Electronegativity
Electrophilicity Index
0.0832013314590371 eV/particle
States of Matter
PhaseGas
Gas PhaseMonoatomic
Boiling Point
87.302 K
Melting Point
83.81 K
Critical Pressure
4.863 MPa
Critical Temperature
150.687 K
Triple Point
83.8058 K
68.89 kPa
Visual

Argon is a Colorless. Ar has a CPK of #ff1493, Jmol of #80d1e3, and MOLCAS GV of #80d1e3. The Appearance of Element 18 is colorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field. The Refractive Index of Argon (Ar) is 1.000281.

Color
Colorless
Appearancecolorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field
Refractive Index
1.000281
Thermodynamic Properties
Thermal Conductivity
0.0177 W/(m K)
Thermal Expansion
Molar Heat Capacity
20.786 J/(mol K)
Specific Heat Capacity
Heat Capacity Ratio (Adiabatic Index)5/3
Electrical Properties
Type
Electrical Conductivity
Electrical Resistivity
Superconducting Point
Magnetism
Typediamagnetic
Magnetic Susceptibility (Mass)
-0.000000006 m³/Kg
Magnetic Susceptibility (Molar)
-0.00000000024 m³/mol
Magnetic Susceptibility (Volume)
-0.0000000107
Magnetic Ordering
Curie Point
Neel Point
Structure

The Crystal Structure of Argon is FCC. The lattice constant of Ar is 5.26 Å. The lattice angles of Element 18 are π/2, π/2, π/2.

Crystal StructureFace Centered Cubic (FCC)
Lattice Constant
5.26 Å
Lattice Anglesπ/2, π/2, π/2
Mechanical Properties

The Speed of Sound of Argon is 319 m/s.

Hardness
Bulk Modulus
Shear Modulus
Young's Modulus
Poisson Ratio
Speed of Sound
319 m/s
Classification

The CAS Group of Argon is VIII. The IUPAC Group of Ar is VIIIA. The Glawe Number of Element 18 is 3. The Mendeleev Number of Argon (Ar) is 114. The Pettifor Number of Argon is 3. The Geochemical Class of Ar is volatile. The Goldschmidt Class of Element 18 is atmophile.

CategoryNoble gases, Noble gases
CAS GroupVIII
IUPAC GroupVIIIA
Glawe Number3
Mendeleev Number114
Pettifor Number3
Geochemical Classvolatile
Goldschmidt Classatmophile

Other

The Gas Basicity of Argon is 346.3 kJ/mol. The Dipole Polarizability of Ar is 11.083 plus or minus 0.007 a₀. Element 18 has a C6 Dispersion Coefficient (CD) of 64.2 a₀, and C6 Dispersion Coefficient (GB) of 67.4 a₀. The Allotropes of Argon (Ar) is . The Neutron Cross Section of Argon is 0.66. The Neutron Mass Absorption of Ar is 0.00059. The Quantum Numbers of Element 18 is 1S0. The Space Group of Argon (Ar) is 225 (Fm_3m).

Gas Basicity
346.3 kJ/mol
Dipole Polarizability
11.083 ± 0.007 a₀
C6 Dispersion Coefficient
64.2 a₀
Allotropes
Neutron Cross Section
0.66
Neutron Mass Absorption
0.00059
Quantum Numbers1S0
Space Group225 (Fm_3m)

Isotopes of Argon

Stable Isotopes2
Unstable Isotopes24
Natural Isotopes3
Isotopic Composition4099.60%4099.60%360.33%360.33%380.06%380.06%

29Ar

Mass Number29
Neutron Number11
Relative Atomic Mass
29.040761 ± 0.000471 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
Spin5/2
Quadrupole Moment
Discovery Year2018
Parity+

Decay ModeIntensity
2p (2-proton emission)100%

30Ar

Mass Number30
Neutron Number12
Relative Atomic Mass
30.023694 ± 0.000192 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
Spin0
Quadrupole Moment
0
Discovery Year2015
Parity+

Decay ModeIntensity
2p (2-proton emission)100%

31Ar

Mass Number31
Neutron Number13
Relative Atomic Mass
31.012158 ± 0.000215 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
15 ± 0.3 ms
Spin5/2
Quadrupole Moment
Discovery Year1986
Parity+

Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)68.3%
2p (2-proton emission)9%
B+pA0.38%
3p0.07%
β+α (β+-delayed α emission)0.03%
2p (2-proton emission)0.0006%

32Ar

Mass Number32
Neutron Number14
Relative Atomic Mass
31.997637824 ± 0.0000019 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
98 ± 2 ms
Spin0
Quadrupole Moment
0
Discovery Year1977
Parity+

Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)35.58%

33Ar

Mass Number33
Neutron Number15
Relative Atomic Mass
32.989925545 ± 0.00000043 Da
G-Factor
-1.446 ± 0.012
Abundance
Radioactivity☢️ Radioactive
Half Life
173 ± 2 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1964
Parity+

Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)38.7%

34Ar

Mass Number34
Neutron Number16
Relative Atomic Mass
33.980270092 ± 0.000000083 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
846.46 ± 0.35 ms
Spin0
Quadrupole Moment
0
Discovery Year1966
Parity+

Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

35Ar

Mass Number35
Neutron Number17
Relative Atomic Mass
34.975257719 ± 0.00000073 Da
G-Factor
0.42133333333333 ± 0.00013333333333333
Abundance
Radioactivity☢️ Radioactive
Half Life
1.7756 ± 0.001 s
Spin3/2
Quadrupole Moment
-0.084 ± 0.015
Discovery Year1940
Parity+

Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

36Ar

Mass Number36
Neutron Number18
Relative Atomic Mass
35.967545106 ± 0.000000028 Da
G-Factor
0
Abundance
0.3336 ± 0.021
Radioactivity☢️ Radioactive
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1920
Parity+

Decay ModeIntensity
+ (double β+ decay)

37Ar

Mass Number37
Neutron Number19
Relative Atomic Mass
36.966776301 ± 0.000000221 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
35.011 ± 0.019 d
Spin3/2
Quadrupole Moment
0.076 ± 0.003
Discovery Year1941
Parity+

Decay ModeIntensity
ϵ (electron capture)100%

38Ar

Mass Number38
Neutron Number20
Relative Atomic Mass
37.962732102 ± 0.000000209 Da
G-Factor
0
Abundance
0.0629 ± 0.007
RadioactivityStable
Half LifeNot Radioactive ☢️
Spin0
Quadrupole Moment
0
Discovery Year1934
Parity+

39Ar

Mass Number39
Neutron Number21
Relative Atomic Mass
38.964313037 ± 0.000005367 Da
G-Factor
-0.45428571428571 ± 0.0042857142857143
Abundance
Radioactivity☢️ Radioactive
Half Life
268 ± 8 y
Spin7/2
Quadrupole Moment
-0.116 ± 0.002
Discovery Year1950
Parity-

Decay ModeIntensity
β (β decay)100%

40Ar

Mass Number40
Neutron Number22
Relative Atomic Mass
39.96238312204 ± 0.00000000234 Da
G-Factor
0
Abundance
99.6035 ± 0.025
RadioactivityStable
Half LifeNot Radioactive ☢️
Spin0
Quadrupole Moment
0
Discovery Year1920
Parity+

41Ar

Mass Number41
Neutron Number23
Relative Atomic Mass
40.96450057 ± 0.000000372 Da
G-Factor
-0.37428571428571 ± 0.0022857142857143
Abundance
Radioactivity☢️ Radioactive
Half Life
109.61 ± 0.04 m
Spin7/2
Quadrupole Moment
-0.042 ± 0.004
Discovery Year1936
Parity-

Decay ModeIntensity
β (β decay)100%

42Ar

Mass Number42
Neutron Number24
Relative Atomic Mass
41.963045737 ± 0.0000062 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
32.9 ± 1.1 y
Spin0
Quadrupole Moment
0
Discovery Year1952
Parity+

Decay ModeIntensity
β (β decay)100%

43Ar

Mass Number43
Neutron Number25
Relative Atomic Mass
42.965636056 ± 0.0000057 Da
G-Factor
-0.4088 ± 0.0024
Abundance
Radioactivity☢️ Radioactive
Half Life
5.37 ± 0.06 m
Spin5/2
Quadrupole Moment
0.142 ± 0.014
Discovery Year1969
Parity

Decay ModeIntensity
β (β decay)100%

44Ar

Mass Number44
Neutron Number26
Relative Atomic Mass
43.964923814 ± 0.0000017 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
11.87 ± 0.05 m
Spin0
Quadrupole Moment
0
Discovery Year1969
Parity+

Decay ModeIntensity
β (β decay)100%

45Ar

Mass Number45
Neutron Number27
Relative Atomic Mass
44.968039731 ± 0.00000055 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
21.48 ± 0.15 s
Spin5/2
Quadrupole Moment
Discovery Year1974
Parity-

Decay ModeIntensity
β (β decay)100%

46Ar

Mass Number46
Neutron Number28
Relative Atomic Mass
45.968039244 ± 0.0000025 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
8.4 ± 0.6 s
Spin0
Quadrupole Moment
0
Discovery Year1974
Parity+

Decay ModeIntensity
β (β decay)100%

47Ar

Mass Number47
Neutron Number29
Relative Atomic Mass
46.972767112 ± 0.0000013 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
1.23 ± 0.03 s
Spin3/2
Quadrupole Moment
Discovery Year1985
Parity

Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)0.2%

48Ar

Mass Number48
Neutron Number30
Relative Atomic Mass
47.976001 ± 0.000018 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
415 ± 15 ms
Spin0
Quadrupole Moment
0
Discovery Year2004
Parity+

Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)38%

49Ar

Mass Number49
Neutron Number31
Relative Atomic Mass
48.981685 ± 0.000429 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
236 ± 8 ms
Spin3/2
Quadrupole Moment
Discovery Year1989
Parity-

Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)29%
2n (2-neutron emission)

50Ar

Mass Number50
Neutron Number32
Relative Atomic Mass
49.985797 ± 0.000537 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
106 ± 6 ms
Spin0
Quadrupole Moment
0
Discovery Year1989
Parity+

Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)37%
2n (2-neutron emission)

51Ar

Mass Number51
Neutron Number33
Relative Atomic Mass
50.993033 ± 0.000429 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year1989
Parity-

Decay ModeIntensity
β (β decay)
β n (β-delayed neutron emission)
2n (2-neutron emission)

52Ar

Mass Number52
Neutron Number34
Relative Atomic Mass
51.998519 ± 0.000644 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
Spin0
Quadrupole Moment
0
Discovery Year2009
Parity+

Decay ModeIntensity
β (β decay)
β n (β-delayed neutron emission)
2n (2-neutron emission)

53Ar

Mass Number53
Neutron Number35
Relative Atomic Mass
53.00729 ± 0.00075 Da
G-Factor
Abundance
Radioactivity☢️ Radioactive
Half Life
Spin5/2
Quadrupole Moment
Discovery Year2009
Parity-

Decay ModeIntensity
β (β decay)
β n (β-delayed neutron emission)
2n (2-neutron emission)

54Ar

Mass Number54
Neutron Number36
Relative Atomic Mass
54.013484 ± 0.000859 Da
G-Factor
0
Abundance
Radioactivity☢️ Radioactive
Half Life
Spin0
Quadrupole Moment
0
Discovery Year2018
Parity+

Decay ModeIntensity
β (β decay)
β n (β-delayed neutron emission)
2n (2-neutron emission)
Argon ice 1

History

Argon was suspected to be present in air by Henry Cavendish in 1785. It was not isolated until 1894 by Lord Rayleigh and Sir William Ramsay in Scotland. Argon became the first member of the noble gases to be discovered. In 1957, IUPAC agreed that the symbol should change from A to Ar. From the Greek argos, inactive

DiscoverersSir William Ramsey, Baron Rayleigh
Discovery LocationScotland
Discovery Year1894
Etymology (Name Origin)Greek: argos (inactive).
PronunciationAR-gon (English)
Argon is considered to be non-toxic
Argon makes a distinctive blue-green gas laser

Uses

Argon gas is used to fill conventional incandescent and fluorescent light bulbs. 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. It is used as a protective atmosphere for growing silicon and germanium crystals. Used in lighting products. It is often used in filling incandescent light bulbs. Some is mixed with krypton in fluorescent lamps. Crystals in the semiconductor industry are grown in argon atmospheres.

Sources

Continuously released into the air by decay of radioactive potassium-40. Pure form is obtained from fractional distillation of liquid air.

Abundance
Abundance in Earth's crust
3.5 mg/kg
Natural Abundance (Oceans)
0.45 mg/L
Natural Abundance (Human Body)
Natural Abundance (Meteor)
Natural Abundance (Sun)
0.007 %
Abundance in Universe
0.02 %

Nuclear Screening Constants

1s0.4925
2p3.9918
2s5.7696
3p11.2359
3s10.2432

Also Known As

  • Ar
  • element 18
  • 18Ar

Translations

  • Italianargon
  • Norwegian Bokmålargon
  • Frenchargon
  • GermanArgon
  • Polishargon
  • Dutchargon
  • Spanishargón
  • Chinese (Traditional)
  • Afrikaansargon
  • Amharicአርገን
  • AragoneseArgón
  • Arabicأرغون
  • AsturianArgón
  • AzerbaijaniArqon
  • BashkirАргон
  • BelarusianАргон
  • Bulgarianаргон
  • Banglaআর্গন
  • BretonArgon
  • Bosnianargon
  • Catalanargó
  • CorsicanArgone
  • Czechargon
  • ChuvashАргон
  • Welshargon
  • Danishargon
  • ZazaArgon
  • Greekαργό
  • Esperantoargono
  • Estonianargoon
  • Basqueargon
  • Persianآرگون
  • Finnishargon
  • Northern FrisianArgon
  • FriulianArgon
  • Western FrisianArgon
  • IrishArgón
  • Galicianargon
  • GuaraniTatapu'ã'ỹ
  • Manxargon
  • Hakka ChineseArgon
  • Hawaiian‘Aragona
  • Hebrewארגון
  • Hindiआर्गन
  • Fiji HindiArgon
  • CroatianArgon
  • Haitian CreoleAgon
  • Hungarianargon
  • Armenianարգոն
  • Interlinguaargon
  • Indonesianargon
  • Idoargono
  • Icelandicargon
  • Japaneseアルゴン
  • Lojbanlaznynavni
  • JavaneseArgon
  • Georgianარგონი
  • KazakhАргон
  • Kannadaಆರ್ಗಾನ್
  • Korean아르곤
  • KomiАргон
  • Latinargon
  • LuxembourgishArgon
  • LimburgishArgon
  • LigurianArgon
  • LithuanianArgonas
  • Latvianargons
  • Māoriargon
  • MacedonianАргон
  • Malayalamആർഗോൺ
  • Mongolianаргон
  • Marathiआरगॉन
  • Western MariАргон
  • Malayargon
  • Low GermanArgon
  • Nepaliआर्गन
  • Norwegian Nynorskargon
  • NavajoNíłchʼi Dootłʼizhí
  • OccitanArgon
  • Punjabiਆਰਗਾਨ
  • PapiamentoArgon
  • Western Panjabiآرگون
  • Portugueseárgon
  • QuechuaArgun
  • Romanianargon
  • Russianаргон
  • RusynАрґон
  • Sicilianargon
  • Serbo-CroatianArgon
  • Sinhalaආගන්
  • Slovakargón
  • Slovenianargon
  • AlbanianArgoni
  • Serbianаргон
  • Saterland FrisianArgon
  • Swedishargon
  • SwahiliArigoni
  • Tamilஆர்கான்
  • Thaiอาร์กอน
  • TagalogArgon
  • TurkishArgon
  • Uyghurئارگون
  • Ukrainianаргон
  • UzbekArgon
  • VepsArgon
  • Vietnameseagon
  • WarayArgon
  • KalmykАрһон
  • Yiddishארגאן
  • YorubaArgon
  • Chinese
  • CebuanoArgon
  • Central Kurdishئارگۆن
  • Odiaଆର୍ଗନ
  • Gujaratiઆર્ગોન
  • Tatarаргон
  • PampangaArgon
  • Scotsargon
  • Chinese (China)
  • Chinese (Hong Kong SAR China)
  • Cantonese
  • Newariआर्गन
  • ErzyaАргон
  • SomaliAargon
  • Literary Chinese
  • Belarusian (Taraskievica orthography)аргон
  • AromanianArgon
  • Church SlavicАргонъ
  • FaroeseArgon
  • KyrgyzАргон
  • cdoĀ
  • Min Nan ChineseArgon
  • Teluguఆర్గాన్
  • Scottish GaelicArgon
  • Sanskritआर्गन
  • LombardArgon
  • Malteseargon
  • Gan Chinese
  • Paliआर्गन
  • English (United Kingdom)argon
  • TajikАргон
  • SundaneseArgon
  • Bhojpuriआर्गन
  • Tibetanགཉུག་རླུང་།
  • Portuguese (Brazil)argônio
  • Lingua Franca Novaargon
  • Tatar (Cyrillic)аргон
  • Burmeseအာဂွန်
  • oloArgon
  • kbpArɩkɔŋ
  • Wu Chinese
  • Chinese (Taiwan)
  • PiedmonteseÀrgon
  • Chinese (Simplified)
  • Chinese (Singapore)
  • Chinese (Malaysia)
  • Chinese (Macao SAR China)
  • SardinianArgòn
  • Moroccan Arabicآرݣون
  • German (Switzerland)Argon
  • English (Canada)Argon
  • Egyptian Arabicارجون
  • Pashtoآرگون
  • BikolArgon
  • CornishArgon
  • Manipuriꯑꯥꯔꯒꯣꯟ
  • BalineseArgon
  • Urduآرگون
  • Sindhiآرگون
  • Malay (Arabic)ارݢون
  • Northern Samiargon
  • Inari Samiargon
  • blkအာဂွန်
  • ZuluIsAlahwe