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Argon Quick Reference

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Notes

Symbol

Ar

Atomic Number

18

Atomic Weight

Rounded

39.95

for regular calculations

Standard

39.948 ± 0.001

for precise calculations

Oxidation States

0

Electron Configuration

Orbital Occupancy

[Ne] 3s2 3p6

[Ne] represents the closed-shell electron configuration of neon

Orbital Filling Order

[Ne] 3s2 3p6

[Ne] represents the closed-shell electron configuration of neon

Term Symbol

1S0

see expanded configuration ...

Ionization Energies

I   (1)

15.759610 eV

II  (2)

27.62966 eV 

III (3)

40.74 eV    

IV  (4)

59.81 eV    

see all 18 energies ...

Electron Affinity

<0 eV

<0 cm-1

Density

gas

400 K, 1 bar

1.2012 g/L

300 K, 1 bar

1.6025 g/L

25 °C, 1 atm

1.6329 g/L

290 K, 1 bar

1.6579 g/L

280 K, 1 bar

1.7174 g/L

273.15 K, 1 atm

1.782 g/L 

270 K, 1 bar

1.7812 g/L

200 K, 1 bar

2.4093 g/L

liquid, 83.78 K

1.419 g/ml

solid, 4 K

1.77 g/cm3

see all 38 densities ...

Molar Volume

gas, 273.15 K, 1 atm

22.4134 L/mol

solid, 0 K, 0 atm

22.56 cm3/mol

Melting Point

7.2 GPa

810 K to 820 K

5.7 GPa

700 K to 750 K

10.0 bar

84.00 K 

5.0 bar

83.87 K 

2.5 bar

83.81 K 

1 bar

83.814 K

Boiling Point

10 bar

116.59 K 

2 bar

 94.28 K 

1.5 bar

 91.18 K 

1 atm

 87.303 K

ITS-90 first-quality, secondary reference point

1 bar

 87.17 K 

0.8 bar

 85.12 K 

Thermal Conductivity

gas

400 K, 1 atm

0.02233 W/(m K)

300 K, 1 atm

0.01772 W/(m K)

290 K, 1 atm

0.01722 W/(m K)

280 K, 1 atm

0.01671 W/(m K)

270 K, 1 atm

0.01619 W/(m K)

200 K, 1 atm

0.01244 W/(m K)

see all 50 conductivities ...

Pyykkö Covalent Radius

single bond

 96 pm

double bond

107 pm

triple bond

 96 pm

Enthalpy of Fusion

1 atm

1.21 kJ/mol

Enthalpy of Vaporization

1 atm

6.53 kJ/mol

Quantity

Argon Atomic Structure

Notes

Ionization Energies

I   (1)

15.759610 eV

II  (2)

27.62966 eV 

III (3)

40.74 eV    

IV  (4)

59.81 eV    

see all 18 energies ...

Electron Affinity

<0 eV

<0 cm-1

Electron Binding Energies

K    (1s)

3205.9 eV

LI   (2s)

 326.3 eV

LII  (2p1/2)

 250.6 eV

LIII (2p3/2)

 248.4 eV

see all 7 energies ...

Electron Configuration

Orbital Occupancy

[Ne] 3s2 3p6

[Ne] represents the closed-shell electron configuration of neon

Orbital Filling Order

[Ne] 3s2 3p6

[Ne] represents the closed-shell electron configuration of neon

Term Symbol

1S0

see expanded configuration ...

Clementi-Raimondi Effective Nuclear Charge

1s

Orbital Exponent

17.5075

ζ

Principle Quantum Number

1

n

Effective Nuclear Charge

17.5075

Zeff = ζ × n

2s

Orbital Exponent

 6.1152

ζ

Principle Quantum Number

2

n

Effective Nuclear Charge

12.230 

Zeff = ζ × n

see all 5 effective nuclear charges ...

Screening Percentage

58.6%

Fluorescence Yields

ωK

0.120  

ωL1

0.00018

ωL2

0.00022

ωL3

0.00022

Coster-Kronig Yields

F12

0.31

F13

0.62

Quantity

Argon Physical Properties

Notes

Density

gas

400 K, 1 bar

1.2012 g/L

300 K, 1 bar

1.6025 g/L

25 °C, 1 atm

1.6329 g/L

290 K, 1 bar

1.6579 g/L

280 K, 1 bar

1.7174 g/L

273.15 K, 1 atm

1.782 g/L 

270 K, 1 bar

1.7812 g/L

200 K, 1 bar

2.4093 g/L

liquid, 83.78 K

1.419 g/ml

solid, 4 K

1.77 g/cm3

see all 38 densities ...

Molar Mass

Rounded

39.95 g/mol

for regular calculations

Standard

39.948 ± 0.001 g/mol

for precise calculations

Molar Volume

gas, 273.15 K, 1 atm

22.4134 L/mol

solid, 0 K, 0 atm

22.56 cm3/mol

Physical Form

colorless gas

Speed of Sound

gas

400 K, 1 bar

372.65 m/s

27 °C, 1 atm

323 m/s   

300 K, 1 bar

322.67 m/s

290 K, 1 bar

317.24 m/s

280 K, 1 bar

311.70 m/s

270 K, 1 bar

306.07 m/s

200 K, 1 bar

263.21 m/s

liquid, -185.9 °C, 1 atm

813 m/s   

see all 35 speeds of sound ...

Dielectric Constant

20 °C, 1 atm

1.00055

140 K

1.32   

-376 °F

1.5    

Isothermal Bulk Modulus

77 K

1.3 GPa

Isothermal Compressibility

77 K

0.79 GPa-1

Gram Atomic Volume

24 cm3

Quantity

Argon Atomic Interaction

Notes

Oxidation States

0

Mulliken-Jaffe Electronegativity

hybridsp3

3.49

hybrid12.5% s

3.19

orbitalp

2.86

Sanderson Electronegativity

3.31

Allred-Rochow Electronegativity

3.20

Configuration Energy

electron volt units

19.17 eV

Pauling units

 3.242  

Allen Electronegativity

3.242

Ghosh-Gupta Electronegativity

7.6515 eV

Nagle Electronegativity

3.18

Cohesive Energy

per mole

7.74 kJ/mol  

per atom

0.080 eV/atom

Quantity

Argon Thermodynamics

Notes

Melting Point

7.2 GPa

810 K to 820 K

5.7 GPa

700 K to 750 K

10.0 bar

84.00 K 

5.0 bar

83.87 K 

2.5 bar

83.81 K 

1 bar

83.814 K

Boiling Point

10 bar

116.59 K 

2 bar

 94.28 K 

1.5 bar

 91.18 K 

1 atm

 87.303 K

ITS-90 first-quality, secondary reference point

1 bar

 87.17 K 

0.8 bar

 85.12 K 

Thermal Conductivity

gas

400 K, 1 atm

0.02233 W/(m K)

300 K, 1 atm

0.01772 W/(m K)

290 K, 1 atm

0.01722 W/(m K)

280 K, 1 atm

0.01671 W/(m K)

270 K, 1 atm

0.01619 W/(m K)

200 K, 1 atm

0.01244 W/(m K)

see all 50 conductivities ...

Triple Point

temperature

83.8058 K

ITS-90 fixed point

pressure

68.891 ± 0.002 kPa

Critical Point

temperature

150.687 ± 0.015 K

pressure

4.863 ± 0.003 MPa

Vapor Pressure

-186.0 °C

100 kPa

-201.7 °C

10 kPa

-212.4 °C

1 kPa

see all 22 pressures ...

Enthalpy of Fusion

1 atm

1.21 kJ/mol

Enthalpy of Vaporization

1 atm

6.53 kJ/mol

Isobaric Molar Heat Capacity

gas

390 K, 1 atm

20.81 J/(mol K)

300 K

1 atm

20.83 J/(mol K)

1 bar

20.83 J/(mol K)

295 K, 1 atm

20.84 J/(mol K)

285 K, 1 atm

20.84 J/(mol K)

275 K, 1 atm

20.85 J/(mol K)

270 K, 1 atm

20.85 J/(mol K)

195 K, 1 atm

20.93 J/(mol K)

see all 56 capacities ...

Isobaric Specific Heat Capacity

gas

400 K, 1 bar

0.52093 J/(g K)

300 K, 1 bar

0.52152 J/(g K)

290 K, 1 bar

0.52162 J/(g K)

280 K, 1 bar

0.52174 J/(g K)

270 K, 1 bar

0.52187 J/(g K)

200 K, 1 bar

0.52364 J/(g K)

see all 33 capacities ...

Isochoric Molar Heat Capacity

gas

390 K, 1 atm

12.48 J/(mol K)

300 K

1 atm

12.48 J/(mol K)

1 bar

12.48 J/(mol K)

295 K, 1 atm

12.48 J/(mol K)

285 K, 1 atm

12.48 J/(mol K)

275 K, 1 atm

12.48 J/(mol K)

270 K, 1 atm

12.48 J/(mol K)

195 K, 1 atm

12.50 J/(mol K)

see all 56 capacities ...

Isochoric Specific Heat Capacity

gas

400 K, 1 bar

0.31229 J/(g K)

300 K, 1 bar

0.31238 J/(g K)

290 K, 1 bar

0.31240 J/(g K)

280 K, 1 bar

0.31242 J/(g K)

270 K, 1 bar

0.31245 J/(g K)

200 K, 1 bar

0.31282 J/(g K)

see all 33 capacities ...

Debye Temperature

Low Temperature Limit ( 0 K )

92.0 K

Quantity

Argon Identification

Notes

CAS Number

7440-37-1

DOT Number

1006

compressed

1006

refrigerated liquid (cryogenic liquid)

1951

ICSC Number

0154

RTECS Number

CF2300000

UN Number

1951

Quantity

Argon Atomic Size

Notes

Orbital Radius

65.9 pm

Pyykkö Covalent Radius

single bond

 96 pm

double bond

107 pm

triple bond

 96 pm

Cordero Covalent Radius

106 pm

Pauling Univalent Radius

ion charge: 0

154 pm

Bondi Van Der Waals Radius

188 pm

Quantity

Argon Crystal Structure

Notes

Allotropes

allotrope

α-argon

symbol

αAr

allotrope

β-argon

symbol

βAr

Nearest Neighbor Distance

4 K, 1 atm

376 pm

Atomic Concentration

4 K, 1 atm

2.66×1022 cm-3

Quantity

Argon History

Notes

Discovery

date of discovery

1894

discoverer

William Ramsay

birth

October 2, 1852

death

July 23, 1916

discoverer

John William Strutt (the third Lord Rayleigh)

birth

November 12, 1842

death

June 30, 1919

location of discovery

London, England

Origin of Element Name

origin

argos

origin description

property—Greek for idle or inactive

Origin of Element Symbol

symbol: Ar

origin

argon

origin description

element name

Formerly Used or Proposed Element Names and Symbols

symbol

A

Quantity

Argon Abundances

Notes

Earth's Crust

3.5 ppm

Earth's Atmosphere

9340 ppm

Ocean Water

0.45 ppm

Solar System

1.01×105

number of atoms for every 106 atoms of silicon

Sun

6.40 ± 0.10

base 10 log of the number of atoms for every 1012 atoms of hydrogen

Quantity

Argon Nomenclature

Notes

Element Names in Other Languages

French

argon

German

Argon

Italian

argo

Spanish

argón

Portuguese

argônio

Anions or Anionic Substituent Groups

argonide

Cations or Cationic Substituent Groups

argon (general)

Ar+, argon(1+)

Ligands

argonido

Heteroatomic Anion

argonate

'a' Term—Substitutive Nomenclature

argona

'y' Term—Chains and Rings Nomenclature

argony

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