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Hydrogen

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Hydrogen Quick Reference

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Notes

Symbol

H

Atomic Number

1

Atomic Weight

Rounded

1.0080

for regular calculations

Standard

1.00784 to 1.00811

for precise calculations

Oxidation States

 1

more common

 0

less common

-1

more common with disagreement

Pauling Electronegativity

2.20

Electron Configuration

Orbital Occupancy

1s1

Orbital Filling Order

1s1

Term Symbol

2S1/2

see expanded configuration ...

Ionization Energies

I (1)

13.598433 eV

Electron Affinity

 0.75420375 ± 0.00000003 eV

6083.064145 ± 0.000030 cm-1

Density

gas

400.0 K, 1 atm

0.06139 g/L

parahydrogen

300.0 K

1 atm

0.08184 g/L

parahydrogen

1 bar

0.08077 g/L

parahydrogen

25 °C, 1 atm

0.0824 g/L 

280.0 K, 1 atm

0.08769 g/L

parahydrogen

273.15 K, 1 atm

0.08995 g/L

270.0 K, 1 atm

0.09093 g/L

parahydrogen

200.0 K, 1 atm

0.1228 g/L 

parahydrogen

liquid, 13.95 K

0.0776 g/ml

solid, 4 K

0.088 g/cm3

see all 58 densities ...

Molar Volume

gas, 273.15 K, 1 atm

22.4135 L/mol 

solid, 0 K, 0 atm

para-H2

23.207 cm3/mol

ortho-D2

19.95 cm3/mol 

T2

18.18 cm3/mol 

HD

21.25 cm3/mol 

HT

19.94 cm3/mol 

DT

18.96 cm3/mol 

Melting Point

146 GPa

 880 ± 50 K

106 GPa

1050 ± 60 K

melting curve maximum

1 atm

14.01 K

1 bar

13.95 K

Boiling Point

1 atm

20.388 K

Normal hydrogen consists of 75% orthohydrogen and 25% parahydrogen. This temperature is an ITS-90 second-quality, secondary reference point.

Thermal Conductivity

gas (normal hydrogen)

400 K, 1 atm

0.2212 W/(m K)

300 K, 1 atm

0.1815 W/(m K)

290 K, 1 atm

0.1767 W/(m K)

280 K, 1 atm

0.1717 W/(m K)

270 K, 1 atm

0.1665 W/(m K)

200 K, 1 atm

0.1280 W/(m K)

see all 56 conductivities ...

Pyykkö Covalent Radius

single bond

32 pm

Atomic Radius

37 pm

Enthalpy of Fusion

1 atm

0.12 kJ/mol

Enthalpy of Vaporization

1 atm

0.46 kJ/mol

Quantity

Hydrogen Atomic Structure

Notes

Ionization Energies

I (1)

13.598433 eV

Electron Affinity

 0.75420375 ± 0.00000003 eV

6083.064145 ± 0.000030 cm-1

Electron Binding Energies

(1s)

13.6 eV

Electron Configuration

Orbital Occupancy

1s1

Orbital Filling Order

1s1

Term Symbol

2S1/2

see expanded configuration ...

Screening Percentage

0.0%

Fluorescence Yields

ωK

0.00002

Quantity

Hydrogen Physical Properties

Notes

Density

gas

400.0 K, 1 atm

0.06139 g/L

parahydrogen

300.0 K

1 atm

0.08184 g/L

parahydrogen

1 bar

0.08077 g/L

parahydrogen

25 °C, 1 atm

0.0824 g/L 

280.0 K, 1 atm

0.08769 g/L

parahydrogen

273.15 K, 1 atm

0.08995 g/L

270.0 K, 1 atm

0.09093 g/L

parahydrogen

200.0 K, 1 atm

0.1228 g/L 

parahydrogen

liquid, 13.95 K

0.0776 g/ml

solid, 4 K

0.088 g/cm3

see all 58 densities ...

Molar Mass

Rounded

1.0080 g/mol

for regular calculations

Standard

1.00784 g/mol to 1.00811 g/mol

for precise calculations

Molar Volume

gas, 273.15 K, 1 atm

22.4135 L/mol 

solid, 0 K, 0 atm

para-H2

23.207 cm3/mol

ortho-D2

19.95 cm3/mol 

T2

18.18 cm3/mol 

HD

21.25 cm3/mol 

HT

19.94 cm3/mol 

DT

18.96 cm3/mol 

Physical Form

colorless gas

Speed of Sound

gas

400.0 K, 1 atm

1518.0 m/s

parahydrogen

300.0 K, 1 atm

1310.0 m/s

parahydrogen

27 °C, 1 atm

1310 m/s  

280.0 K, 1 atm

1263.0 m/s

parahydrogen

270.0 K, 1 atm

1239.0 m/s

parahydrogen

200.0 K, 1 atm

1054.0 m/s

parahydrogen

see all 57 speeds of sound ...

Dielectric Constant

440 °F

1.23   

20 °C, 1 atm

1.00025

13.52 K

1.28   

deuterium, 68 °F

1.3    

Isothermal Bulk Modulus

4 K

0.2 GPa

Isothermal Compressibility

4 K

5 GPa-1

Gram Atomic Volume

13 cm3

Quantity

Hydrogen Atomic Interaction

Notes

Oxidation States

 1

more common

 0

less common

-1

more common with disagreement

Pauling Electronegativity

2.20

Mulliken-Jaffe Electronegativity

orbitals

2.25

Sanderson Electronegativity

2.592

Allred-Rochow Electronegativity

2.20

Configuration Energy

electron volt units

13.61 eV

Pauling units

 2.300  

Allen Electronegativity

2.300

Allred Electronegativity

oxidation state: 1

2.20

Ghosh-Gupta Electronegativity

7.1862 eV

Nagle Electronegativity

2.27

Pearson Absolute Electronegativity

7.18 eV

Smith Electronegativity

oxidation state: 1

2.1

oxidation state: -1

2.0

Chemical Hardness

6.43 eV

Quantity

Hydrogen Thermodynamics

Notes

Melting Point

146 GPa

 880 ± 50 K

106 GPa

1050 ± 60 K

melting curve maximum

1 atm

14.01 K

1 bar

13.95 K

Boiling Point

1 atm

20.388 K

Normal hydrogen consists of 75% orthohydrogen and 25% parahydrogen. This temperature is an ITS-90 second-quality, secondary reference point.

Thermal Conductivity

gas (normal hydrogen)

400 K, 1 atm

0.2212 W/(m K)

300 K, 1 atm

0.1815 W/(m K)

290 K, 1 atm

0.1767 W/(m K)

280 K, 1 atm

0.1717 W/(m K)

270 K, 1 atm

0.1665 W/(m K)

200 K, 1 atm

0.1280 W/(m K)

see all 56 conductivities ...

Triple Point

equilibrium

temperature

13.8033 K

Equilibrium hydrogen near this temperature consists of 0.21% orthohydrogen and 99.79% parahydrogen. This temperature is an ITS-90 fixed point.

pressure

7.030 kPa

normal

temperature

13.952 K

Normal hydrogen consists of 75% orthohydrogen and 25% parahydrogen. This temperature is an ITS-90 second-quality, secondary reference point.

pressure

7.200 kPa

deuterium

equilibrium

temperature

18.689 K

Equilibrium deuterium at the triple point consists of 98.5% orthohydrogen and 1.5% parahydrogen. This temperature is an ITS-90 first-quality, secondary reference point.

pressure

17.130 kPa

normal

temperature

18.724 K

Normal deuterium at the triple point consists of 66.7% orthohydrogen and 33.3% parahydrogen. This temperature is an ITS-90 first-quality, secondary reference point.

pressure

17.150 kPa

tritium

temperature

20.62 K

pressure

21.6 kPa

Critical Point

equilibrium

temperature

32.976 K

pressure

1.293 MPa

normal

temperature

33.19 K

pressure

1.315 MPa

deuterium

equilibrium

temperature

38.262 K

pressure

1.650 MPa

normal

temperature

38.34 K

pressure

1.665 MPa

tritium

temperature

40.44 K

estimate

pressure

1.850 MPa

Vapor Pressure

-252.8 °C

100 kPa

-258.6 °C

10 kPa

14 K

7.90 kPa

see all 22 pressures ...

Enthalpy of Fusion

1 atm

0.12 kJ/mol

Enthalpy of Vaporization

1 atm

0.46 kJ/mol

Isobaric Molar Heat Capacity

gas

400.0 K, 1 atm

29.33 J/(mol K) 

parahydrogen

300.0 K

1 atm

29.93 J/(mol K) 

parahydrogen

1 bar

29.93 J/(mol K) 

parahydrogen

298.15 K, 1 bar

28.836 J/(mol K)

280.0 K, 1 atm

30.23 J/(mol K) 

parahydrogen

270.0 K, 1 atm

30.43 J/(mol K) 

parahydrogen

see all 54 capacities ...

Isobaric Specific Heat Capacity

298.15 K, 1 bar

14.304 J/(g K)

Isochoric Molar Heat Capacity

gas

400.0 K, 1 bar

21.02 J/(mol K)

parahydrogen

300 K, 1 bar

21.61 J/(mol K)

parahydrogen

280.0 K, 1 bar

21.92 J/(mol K)

parahydrogen

270 K, 1 bar

22.11 J/(mol K)

parahydrogen

200 K, 1 bar

24.08 J/(mol K)

parahydrogen

see all 57 capacities ...

Debye Temperature

Low Temperature Limit ( 0 K )

122 K

Quantity

Hydrogen Identification

Notes

CAS Number

1333-74-0

DOT Number

1049

absorbed in metal hydride

9279

compressed

1049

in a metal hydride storage system

3468

in a metal hydride storage system contained in equipment

3468

in a metal hydride storage system packed with equipment

3468

refrigerated liquid (cryogenic liquid)

1966

ICSC Number

0001

RTECS Number

MW8900000

UN Number

1049

Quantity

Hydrogen Atomic Size

Notes

Atomic Radius

37 pm

Orbital Radius

52.9 pm

Pyykkö Covalent Radius

single bond

32 pm

Cordero Covalent Radius

31 pm

Shannon-Prewitt Crystal Radius

ion charge: +1

coordination number: 1

-24 pm

coordination number: 2

 -4 pm

Shannon-Prewitt Effective Ionic Radius

ion charge: +1

coordination number: 1

-38 pm

coordination number: 2

-18 pm

Pauling Empirical Crystal Radius

ion charge: -1

208 pm

Pauling Univalent Radius

ion charge: -1

208 pm

Bondi Van Der Waals Radius

120 pm

Pauling Van Der Waals Radius

1.2×102 pm

Slater Atomic-Ionic Radius

25 pm

Quantity

Hydrogen Crystal Structure

Notes

Allotropes

allotrope

α-hydrogen

symbol

αH

allotrope

β-hydrogen

symbol

βH

Quantity

Hydrogen History

Notes

Discovery

date of discovery

1766

discoverer

Henry Cavendish

birth

October 10, 1731

death

February 24, 1810

location of discovery

London, England

Origin of Element Name

origin

hydros gen

origin description

property—Greek for water producing

Origin of Element Symbol

symbol: H

origin

hydrogen

origin description

element name

Quantity

Hydrogen Abundances

Notes

Earth's Crust

1.40×103 ppm

Earth's Mantle

0.012%

primitive mantle

Earth's Core

600 ppm

Bulk Earth

260 ppm

Earth's Atmosphere

0.55 ppm

H2

Ocean Water

1.078×105 ppm

River Water

1.119×105 ppm

U.S. Coal

5.2%

Human Body

7 kg

based on a 70 kg "reference man"

Human Bone

52×103 ppm

Human Hair

29×103 ppm

Human Kidney

93×103 ppm

Human Liver

93×103 ppm

Human Muscle

93×103 ppm

Human Nail

29×103 ppm

Bacteria

74×103 ppm

Ferns

55×103 ppm

Fungi

55×103 ppm

Universe

1.00000

relative to hydrogen = 1.00000

Solar System

2.79×1010

number of atoms for every 106 atoms of silicon

Sun

12.00

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

Halley's Comet

2025 ± 385 atoms

number of atoms for every 100 atoms of magnesium

Quantity

Hydrogen Nomenclature

Notes

Element Names in Other Languages

French

hydrogène

German

Wasserstoff

Italian

idrogeno

Spanish

hidrógeno

Portuguese

hidrogênio

Anions or Anionic Substituent Groups

hydride (general)

H-, hydride (natural or unspecified isotopic composition)

1H-, protide

2H- = D-, deuteride

3H- = T-, tritide

Cations or Cationic Substituent Groups

hydrogen (general)

H+, hydrogen(1+), hydron (natural or unspecified isotopic composition)

1H+, protium(1+), proton

2H+ = D+, deuterium(1+), deuteron

3H+ = T+, tritium(1+), triton

Ligands

hydrido

protido

deuterido

tritido

Heteroatomic Anion

hydrogenate

'y' Term—Chains and Rings Nomenclature

hydrony

References    (Click the button next to a value above to see complete citation information for that entry)

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