Helium

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Helium Quick Reference

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Notes

Symbol

He

Atomic Number

2

Atomic Weight

Rounded

4.003

for regular calculations

Standard

4.002602 ± 0.000002

for precise calculations

Oxidation States

0

Electron Configuration

Orbital Occupancy

1s2

Orbital Filling Order

1s2

Term Symbol

1S0

see expanded configuration ...

Ionization Energies

I  (1)

24.587387 eV

II (2)

54.417760 eV

Electron Affinity

<0 eV

<0 cm-1

Density

gas

25 °C, 1 atm

0.1636 g/L 

273.15 K, 1 atm

0.1786 g/L 

solid, 2 K, 37 atm

0.205 g/cm3

helium-4, liquid

4.21 K

0.125 g/ml 

1.76 K

0.152 g/ml 

helium-3, liquid, 3.19 K

0.055 g/ml 

Molar Volume

gas, 273.15 K, 1 atm

22.4136 L/mol

Melting Point

26 atm

0.95 K

33.3 bar

1.86 K

Boiling Point

1 atm

4.22 K

helium-4, 1 atm

4.21 K

helium-3, 1 atm

3.19 K

Thermal Conductivity

gas

400 K, 1 atm

0.1870 W/(m K)

300 K, 1 atm

0.1520 W/(m K)

290 K, 1 atm

0.1484 W/(m K)

280 K, 1 atm

0.1447 W/(m K)

270 K, 1 atm

0.1411 W/(m K)

200 K, 1 atm

0.1151 W/(m K)

see all 55 conductivities ...

Pyykkö Covalent Radius

single bond

46 pm

Enthalpy of Vaporization

1 atm

0.082 kJ/mol

Quantity

Helium Atomic Structure

Notes

Ionization Energies

I  (1)

24.587387 eV

II (2)

54.417760 eV

Electron Affinity

<0 eV

<0 cm-1

Electron Binding Energies

(1s)

24.6 eV

Electron Configuration

Orbital Occupancy

1s2

Orbital Filling Order

1s2

Term Symbol

1S0

see expanded configuration ...

Clementi-Raimondi Effective Nuclear Charge

1s

Orbital Exponent

1.6875

ζ

Principle Quantum Number

1

n

Effective Nuclear Charge

1.6875

Zeff = ζ × n

Screening Percentage

15.0%

Fluorescence Yields

ωK

0.0001

Quantity

Helium Physical Properties

Notes

Density

gas

25 °C, 1 atm

0.1636 g/L 

273.15 K, 1 atm

0.1786 g/L 

solid, 2 K, 37 atm

0.205 g/cm3

helium-4, liquid

4.21 K

0.125 g/ml 

1.76 K

0.152 g/ml 

helium-3, liquid, 3.19 K

0.055 g/ml 

Molar Mass

Rounded

4.003 g/mol

for regular calculations

Standard

4.002602 ± 0.000002 g/mol

for precise calculations

Molar Volume

gas, 273.15 K, 1 atm

22.4136 L/mol

Physical Form

colorless gas

Speed of Sound

gas

273.2 K

971.9 m/s

0 °C, 1 atm

965 m/s  

liquid

-268.9 °C

180 m/s  

-269 °C, longitudinal wave

211 m/s  

Dielectric Constant

liquid

1.05    

20 °C, 1 atm

1.000068

2.06 K

1.06    

helium-3, 58 °F

1.065   

Gram Atomic Volume

32 cm3

Quantity

Helium Atomic Interaction

Notes

Oxidation States

0

Mulliken-Jaffe Electronegativity

orbitals

3.49

Allred-Rochow Electronegativity

5.50

Configuration Energy

electron volt units

24.59 eV

Pauling units

 4.160  

Ghosh-Gupta Electronegativity

12.0568 eV

Nagle Electronegativity

3.92

Quantity

Helium Thermodynamics

Notes

Melting Point

26 atm

0.95 K

33.3 bar

1.86 K

Boiling Point

1 atm

4.22 K

helium-4, 1 atm

4.21 K

helium-3, 1 atm

3.19 K

Thermal Conductivity

gas

400 K, 1 atm

0.1870 W/(m K)

300 K, 1 atm

0.1520 W/(m K)

290 K, 1 atm

0.1484 W/(m K)

280 K, 1 atm

0.1447 W/(m K)

270 K, 1 atm

0.1411 W/(m K)

200 K, 1 atm

0.1151 W/(m K)

see all 55 conductivities ...

Critical Point

helium-4

temperature

5.19 K

pressure

2.29 bar

helium-3

temperature

3.32 K

pressure

1.16 bar

Vapor Pressure

-268.9 °C

100 kPa

2.5 K

10.23 kPa

2.0 K

3.130 kPa

see all 21 pressures ...

Enthalpy of Vaporization

1 atm

0.082 kJ/mol

Isobaric Molar Heat Capacity

298.15 K, 1 bar

20.786 J/(mol K)

Isobaric Specific Heat Capacity

298.15 K, 1 bar

5.193 J/(g K)

Quantity

Helium Identification

Notes

CAS Number

7440-59-7

DOT Number

1046

compressed

1046

refrigerated liquid (cryogenic liquid)

1963

ICSC Number

0603

RTECS Number

MH6520000

UN Number

1963

Quantity

Helium Atomic Size

Notes

Orbital Radius

29.1 pm

Pyykkö Covalent Radius

single bond

46 pm

Cordero Covalent Radius

28 pm

Pauling Univalent Radius

ion charge: 0

93 pm

Bondi Van Der Waals Radius

140 pm

Quantity

Helium Crystal Structure

Notes

Allotropes

allotrope

α-helium

symbol

αHe

allotrope

β-helium

symbol

βHe

allotrope

γ-helium

symbol

γHe

Quantity

Helium History

Notes

Discovery

date of discovery

1895

discoverer

William Ramsay

birth

October 2, 1852

death

July 23, 1916

location of discovery

London, England

Origin of Element Name

origin

Helios

origin description

celestial body—Greek for Sun

Origin of Element Symbol

symbol: He

origin

helium

origin description

element name

Quantity

Helium Abundances

Notes

Earth's Crust

8×10-3 ppm

Earth's Atmosphere

5.24 ppm

Ocean Water

7.2×10-6 ppm

Universe

0.097

relative to hydrogen = 1.00000

Solar System

2.72×109

number of atoms for every 106 atoms of silicon

Sun

10.93 ± 0.004

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

Quantity

Helium Nomenclature

Notes

Element Names in Other Languages

French

hélium

German

Helium

Italian

elio

Spanish

helio

Portuguese

hélio

Anions or Anionic Substituent Groups

helide

Cations or Cationic Substituent Groups

helium (general)

He•+, helium(•1+)

Ligands

helido

Heteroatomic Anion

helate

'a' Term—Substitutive Nomenclature

hela

'y' Term—Chains and Rings Nomenclature

hely

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

Allen, Leland C., and James E. Huheey. "The Definition of Electronegativity and the Chemistry of the Noble Gases." Journal of Inorganic and Nuclear Chemistry, volume 42, number 10, 1980, pp. 1523–1524. doi:10.1016/0022-1902(80)80132-1

Anders, Edward, and Nicolas Grevesse. "Abundances of the Elements: Meteoritic and Solar." Geochimica et Cosmochimica Acta, volume 53, number 1, 1989, pp. 197–214. doi:10.1016/0016-7037(89)90286-X

Andersen, T., H. K. Haugen, and H. Hotop. "Binding Energies in Atomic Negative Ions: III." Journal of Physical and Chemical Reference Data, volume 28, number 6, 1999, pp. 1511–1533.

Bondi, A. "Van der Waals Volumes and Radii." The Journal of Physical Chemistry, volume 68, number 3, 1964, pp. 441–451. doi:10.1021/j100785a001

Bratsch, Steven G. "Revised Mulliken Electronegativities: I. Calculation and Conversion to Pauling Units." Journal of Chemical Education, volume 65, number 1, 1988, pp. 34–41. doi:10.1021/ed065p34

Cardona, M., and L. Ley, editors. Photoemission in Solids I: General Principles. Berlin: Springer-Verlag, 1978.

Chauvin, Remi. "Explicit Periodic Trend of van der Waals Radii." The Journal of Physical Chemistry, volume 96, number 23, 1992, pp. 9194–9197. doi:10.1021/j100202a023

Clementi, E., and D. L. Raimondi. "Atomic Screening Constants from SCF Functions." Journal of Chemical Physics, volume 38, number 11, 1963, pp. 2686–2689. doi:10.1063/1.1733573

Cohen, E. Richard, David R. Lide, and George L. Trigg, editors. AlP Physics Desk Reference, 3rd edition. New York: Springer-Verlag New York, Inc., 2003.

Connelly, Neil G., Ture Damhus, Richard M. Hartshorn, and Alan T. Hutton. Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005. Cambridge: RSC Publishing, 2005.

Cordero, Beatriz, Verónica Gómez, Ana E. Platero-Prats, Marc Revés, Jorge Echeverría, Eduard Cremades, Flavia Barragán, and Santiago Alvarez. "Covalent Radii Revisited." Dalton Transactions, number 21, 2008, pp 2832–2838. doi:10.1039/b801115j

Cox, P. A. The Elements: Their Origin, Abundance and Distribution. Oxford: Oxford University Press, 1989.

Croswell, Ken. The Alchemy of the Heavens. New York: Anchor Books, 1995.

de Podesta, Michael. Understanding the Properties of Matter, 2nd edition. London: Taylor & Francis, 2002.

Emsley, John. Nature's Building Blocks: An A-Z Guide to the Elements. Oxford: Oxford University Press, 2003.

Emsley, John. The Elements, 3rd edition. Oxford: Oxford University Press, 1998.

Enss, Christian, and Siegfried Hunklinger. Low-Temperature Physics. Berlin: Springer-Verlag, 2005.

Firestone, Richard B. Table of Isotopes, 8th edition, volume 2. Edited by Virginia S. Shirley, with assistant editors Coral M. Baglin, S. Y. Frank Chu, and Jean Zipkin. New York: John Wiley & Sons, Inc., 1996.

Ghosh, Dulal C., and Kartick Gupta. "A New Scale Of Electronegativity Of 54 Elements Of Periodic Table Based On Polarizability Of Atoms." Journal of Theoretical and Computational Chemistry, volume 5, number 4, 2006, pp. 895–911. doi:10.1142/S0219633606002726

Griffiths, David J. Introduction to Electrodynamics, 2nd edition. Upper Saddle River, NJ: Prentice-Hall Inc., 1989.

Gwyn Williams. Electron Binding Energies. http://www.jlab.org/~gwyn/ebindene.html. Accessed on April 30, 2010.

Ho, C. Y., R. W. Powell, and P. E. Liley. "Thermal Conductivity of the Elements: A Comprehensive Review." Journal of Physical and Chemical Reference Data, volume 3, supplement 1, 1974, pp. I–1 to I–796.

Huheey, James E., Ellen A. Keiter, and Richard L Keiter. Inorganic Chemistry: Principles of Structure and Reactivity, 4th edition. New York: HarperCollins College Publishers, 1993.

International Labour Organization (ILO). International Chemical Safety Card for Helium. http://www.ilo.org/legacy/english/protection/safework/cis/products/icsc/dtasht/_icsc06/icsc0603.htm. Accessed on May 4, 2010.

International Labour Organization (ILO). International Chemical Safety Card for Helium. http://www.ilo.org/legacy/english/protection/safework/cis/products/icsc/dtasht/_icsc06/icsc0603.htm. Accessed on May 5, 2010.

Jensen, William B. "Why Helium Ends in “-ium”." Journal of Chemical Education, volume 81, number 7, 2004, p. 944. doi:10.1021/ed081p944

King, H. W. "Pressure-Dependent Allotropic Structures of the Elements." Bulletin of Alloy Phase Diagrams, volume 4, number 4, 1983, pp. 449–450. doi:10.1007/BF02868110

Kittel, Charles. Introduction to Solid State Physics, 8th edition. Hoboken, NJ: John Wiley & Sons, Inc, 2005.

Liboff, Richard L. Introductory Quantum Mechanics, 3rd edition. Reading, MA: Addison Wesley Longman, Inc., 1998.

Lide, David R., editor. CRC Handbook of Chemistry and Physics, 88th edition. Boca Raton, Florida: Taylor & Francis Group, 2008.

Mann, Joseph B., Terry L. Meek, and Leland C. Allen. "Configuration Energies of the Main Group Elements." Journal of the American Chemical Society, volume 122, number 12, 2000, pp. 2780–2783. doi:10.1021/ja992866e

Manuel, O., editor. Origin of Elements in the Solar System: Implications of Post-1957 Observations. New York: Kluwer Academic Publishers, 2000.

Marshall, James L. Discovery of the Elements: A Search for the Fundamental Principles of the Universe, 2nd edition. Boston, MA: Pearson Custom Publishing, 2002.

Martin, W. C. "Electronic Structure of the Elements." The European Physical Journal C — Particles and Fields, volume 15, number 1–4, 2000, pp. 78–79. doi:10.1007/BF02683401

Mechtly, Eugene A. "Properties of Materials." pp. 4–1 to 4–33 in Reference Data For Engineers: Radio, Electronics, Computer, and Communications. By Mac E. Van Valkenburg, edited by Wendy M. Middleton. Woburn, MA: Butterworth-Heinemann, 2002. doi:10.1016/B978-075067291-7/50006-6

Miessler, Gary L., and Donald A. Tarr. Inorganic Chemistry, 3rd edition. Upper Saddle River, NJ: Pearson Prentice Hall, 2004.

Nagle, Jeffrey K. "Atomic Polarizability and Electronegativity." Journal of the American Chemical Society, volume 112, number 12, 1990, pp. 4741–4747. doi:10.1021/ja00168a019

National Aeronautics and Space Administration (NASA). Earth Fact Sheet. http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html. Accessed on September 18, 2011.

National Institute for Occupational Safety and Health (NIOSH). International Chemical Safety Card for Helium. http://www.cdc.gov/niosh/ipcsneng/neng0603.html. Accessed on May 5, 2010.

National Institute for Occupational Safety and Health (NIOSH). International Chemical Safety Card for Helium. http://www.cdc.gov/niosh/ipcsneng/neng0603.html. Accessed on May 4, 2010.

National Institute for Occupational Safety and Health (NIOSH). The Registry of Toxic Effects of Chemical Substances for Helium. http://www.cdc.gov/niosh-rtecs/mh637cc0.html. Accessed on May 5, 2010.

Nobel Foundation. Sir William Ramsay: The Nobel Prize in Chemistry 1904. http://nobelprize.org/nobel_prizes/chemistry/laureates/1904/ramsay-bio.html. Accessed on July 16, 2009.

Oxtoby, David W., H. P. Gillis, and Alan Campion. Principles of Modern Chemistry, 6th edition. Belmont, CA: Thomson Brooks/Cole, 2008.

Pauling, Linus. The Nature of the Chemical Bond, 3rd edition. Ithaca, NY: Cornell University Press, 1960.

Pekka Pyykkö. Self-Consistent, Year-2009 Covalent Radii. http://www.chem.helsinki.fi/~pyykko/Radii09.pdf. Accessed on November 20, 2010.

Pyykkö, Pekka, and Michiko Atsumi. "Molecular Double-Bond Covalent Radii for Elements Li-E112." Chemistry - A European Journal, volume 15, number 46, 2009, pp. 12770–12779. doi:10.1002/chem.200901472

Pyykkö, Pekka, and Michiko Atsumi. "Molecular Single-Bond Covalent Radii for Elements 1-118." Chemistry - A European Journal, volume 15, number 1, 2009, pp. 186–197. doi:10.1002/chem.200800987

Ringnes, Vivi. "Origin of the Names of Chemical Elements." Journal of Chemical Education, volume 66, number 9, 1989, pp. 731–738. doi:10.1021/ed066p731

Rohrer, Gregory S. Structure and Bonding in Crystalline Materials. Cambridge: Cambridge University Press, 2001.

Sansonetti, J. E., and W. C. Martin. "Handbook of Basic Atomic Spectroscopic Data." Journal Of Physical And Chemical Reference Data, volume 34, number 4, 2005, pp. 1559–2259. doi:10.1063/1.1800011

Scientific Group Thermodata Europe (SGTE). Pure Substances: Part 1—Elements and Compounds from AgBr to Ba3N2. Edited by I. Hurtado and D. Neuschütz. Berlin: Springer-Verlag, 1999. doi:10.1007/10652891_3

Silbey, Robert J., Robert A. Alberty, and Moungi G. Bawendi. Physical Chemistry, 4th edition. Hoboken, NJ: John Wiley & Sons, Inc., 2005.

Speight, James G. Perry's Standard Tables and Formulas for Chemical Engineers. New York: The McGraw-Hill Companies, Inc., 2003.

Syshchenko, O., J. Day, and J. Beamish. "Elastic Properties of Solid Helium." Journal of Physics: Condensed Matter, volume 21, number 16, 2009, 164204 (6pp). doi:10.1088/0953-8984/21/16/164204

U. S. Department of Transportation (DOT), Transport Canada (TC), Secretariat of Transport and Communications of Mexico (SCT), and Centro de Información Química para Emergencias (CIQUIME). 2008 Emergency Response Guidebook.

Waber, J. T., and Don T. Cromer. "Orbital Radii of Atoms and Ions." Journal of Chemical Physics, volume 42, number 12, 1965, pp. 4116–4123. doi:10.1063/1.1695904

Wagman, Donald D., William H. Evans, Vivian B. Parker, Richard H. Schumm, Iva Halow, Sylvia M. Bailey, Kenneth L. Churney, and Ralph L. Nuttall. "Thermal Conductivity of the Elements: A Comprehensive Review." Journal of Physical and Chemical Reference Data, volume 11, supplement 2, 1982, pp. 2–1 to 2–392.

Waldron, Kimberley A., Erin M. Fehringer, Amy E. Streeb, Jennifer E. Trosky, and Joshua J. Pearson. "Screening Percentages Based on Slater Effective Nuclear Charge as a Versatile Tool for Teaching Periodic Trends." Journal of Chemical Education, volume 78, number 5, 2001, pp. 635–639. doi:10.1021/ed078p635

Weeks, Mary Elvira, and Henry M. Leicester. Discovery of the Elements, 7th edition. Easton, PA: Journal of Chemical Education, 1968.

Wieser, Michael E., and Tyler B. Coplen. "Atomic weights of the elements 2009 (IUPAC Technical Report)." Pure and Applied Chemistry, volume 83, number 2, 2011, pp. 359–396. doi:10.1351/PAC-REP-10-09-14

Yaws, Carl L. "Liquid Density of the Elements." Chemical Engineering, volume 114, number 12, 2007, pp. 44–46.