Technical data for Helium

Overview
NameHelium
SymbolHe
Atomic Number2
Atomic Weight4.002602
Density0.1785 g/l[note]
Melting PointN/A[note]
Boiling Point-268.93 °C

Thermal properties
PhaseGas
Melting PointN/A[note]
Boiling Point-268.93 °C
Absolute Melting PointN/A[note]
Absolute Boiling Point4.22 K
Critical Presure0.227 MPa (2.24 Atm)
Critical Temperature5.19 K
Heat of Fusion0.02 kJ/mol
Heat of Vaporization0.083 kJ/mol
Heat of CombustionN/A
Specific Heat5193.1 J/(kg K)[note]
Adiabatic Index5/3
Thermal Conductivity0.1513 W/(m K)
Thermal ExpansionN/A

Bulk physical properties
Density0.1785 g/l[note]
Density (Liquid)N/A
Molar Volume0.022424
Refractive Index1.000035
Speed of Sound970 m/s
Thermal Conductivity0.1513 W/(m K)
Thermal ExpansionN/A

Reactivity
Valence0
ElectronegativityN/A
ElectronAffinity0 kJ/mol
Ionization Energies
2372.3, 5250.5 kJ/mol

Health and Safety
Autoignition PointN/A
FlashpointN/A

Classifications
Alternate NamesNone
Nams of AllotropesNone
Blockp
Group18
Period1
Electron Configuration1s2
ColorColorless
Discovery
1895 in Sweden and United Kingdom
Gas phaseMonoatomic
CAS NumberCAS7440-59-7

Electrical properties
Electrical TypeN/A
Electrical ConductivityN/A
ResistivityN/A
Superconducting PointN/A

Magnetic properties
Magnetic TypeDiamagnetic
Curie PointN/A
Mass Magnetic Susceptibility-5.9×10-9
Molar Magnetic Susceptibility-2.36×10-11
Volume Magnetic Susceptibility-1.05×10-9

Abundances
% in Universe23%
% in Sun23%
% in MeteoritesN/A
% in Earth's Crust5.5×10-7%
% in Oceans7.2×10-10%
% in HumansN/A

Atomic dimensions and structure
Atomic Radius31 pm
Covalent Radius32 pm
Van der Waals Radius140 pm
Crystal StructureFace Centered Cubic
Lattice Angles
π/2, π/2, π/2
Lattice Constants
424.2, 424.2, 424.2 pm
Space Group NameFm_ 3m
Space Group Number225

Nuclear Properties
Half-LifeStable
LifetimeStable
Quantum Numbers1S0
Stable Isotopes
3He, 4He
Isotopic Abundances
3He0.000137%
4He99.999863%

Notes on the properties of Helium:

Absolute Melting Point: Helium does not solidify at standard pressure.
Density: Density at 0° Celsius.
Melting Point: Helium does not solidify at standard pressure.
Specific Heat: Value given for gas phase.