Template:Infobox helium

Helium,  ₂He

Template:Infobox element/symbol-to-top-image-caption
General properties
Pronunciation	Template:Infobox element/pronunciation
Appearance	colorless gas, exhibiting a red-orange glow when placed in an electric field
Standard atomic weight (Ar, standard)	Template:Infobox element/standard atomic weight
Mass number	Template:Infobox element/symbol-to-most-stable-isotope (most stable isotope)
Helium in the periodic table
Template:Infobox element/periodic table
Atomic number (Z)	2
Group	Template:Infobox element/group
Period	period 1
Block	s-block
Element category	Template:Infobox element/category format
Electron configuration	1s2
Electrons per shell	2
Physical properties
Phase at STP	gas
Melting point	0.95 K ​(−272.20 °C, ​−457.96 °F) (at 2.5 MPa)
Boiling point	4.222 K ​(−268.928 °C, ​−452.070 °F)
Density (at STP)	0.1786 g/L
when liquid (at m.p.)	0.145 g/cm3
when liquid (at b.p.)	0.125 g/cm3
Triple point	2.177 K, ​5.043 kPa
Critical point	5.1953 K, 0.22746 MPa
Heat of fusion	0.0138 kJ/mol
[[Enthalpy of vaporization|Heat of Template:Engvar]]	0.0829 kJ/mol
Molar heat capacity	20.78 J/(mol·K)
[[Vapor pressure|Template:Engvar pressure]] (defined by ITS-90) Template:Infobox element/vapor pressure table
Atomic properties
Oxidation states	Template:Infobox element/symbol-to-oxidation-state
Electronegativity	Pauling scale: no data
[[Ionization energy|Template:Engvar energies]]	1st: 2372.3 kJ/mol 2nd: 5250.5 kJ/mol
Covalent radius	28 pm
Van der Waals radius	140 pm
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Other properties
Crystal structure	​Template:Infobox element/crystal structure Template:Infobox element/crystal structure
Speed of sound	972 m/s
Thermal conductivity	0.1513 W/(m·K)
Magnetic ordering	diamagnetic
Magnetic susceptibility	−1.88·10−6 cm3/mol (298 K)
CAS Number	7440-59-7
History
Naming	after Helios, Greek Titan of the Sun
Discovery	Pierre Janssen, Norman Lockyer (1868)
First isolation	William Ramsay, Per Teodor Cleve, Abraham Langlet (1895)
Main isotopes of helium
Template:Infobox element/isotopes table

Template:Infobox element/element navigation Template:Template reference list One of these is a named reference. It may be cited in the containing article as

• <ref name="CIAAW2016" /> for the source Atomic weights of the elements 2013 (from subtemplates used by {{Infobox element}})

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