View source for Template:Infobox helium/sandbox

{{Infobox element/sandbox
|name=helium
|number=2
|symbol=He
|pronounce={{IPAc-en|ˈ|h|iː|l|i|ə|m}}
|pronounce 2={{respell|HEE|lee-əm}}
|left=[[hydrogen]]
|right=[[lithium]]
|above=-
|below=[[neon|Ne]]
|category=noble gas
|category comment=
|group=18
|period=1
|block=s
|category color=
|appearance=colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field
|image name=Helium discharge tube.jpg
|image name comment=
|image name 2=Helium spectra.jpg
|image name 2 comment=Spectral lines of helium
|standard atomic weight={{val|4.002602|(2)}}
|standard atomic weight ref={{CIAAW2016}}
|electron configuration=1s<sup>2</sup>
|electrons per shell=2
|color=
|phase=gas
|phase comment=
|density gplstp=0.1786
|density gpcm3nrt=
|density gpcm3bp=0.125
|density gpcm3mp=0.145
|melting point K=0.95
|melting point C=−272.20
|melting point F=−457.96
|melting point comment=(at&nbsp;2.5&nbsp;MPa)
|boiling point K=4.222
|boiling point C=−268.928
|boiling point F=−452.070
|triple point K=2.177
|triple point kPa=5.043
|critical point K=5.1953
|critical point MPa=0.22746
|heat fusion=0.0138
|heat vaporization=0.0829
|heat capacity=5[[Gas constant|R]]/2 = 20.786
|vapor pressure 1=&nbsp;
|vapor pressure 10=&nbsp;
|vapor pressure 100=1.23
|vapor pressure 1 k=1.67
|vapor pressure 10 k=2.48
|vapor pressure 100 k=4.21
|vapor pressure comment=(defined by [[International Temperature Scale of 1990|ITS-90]])
|crystal structure=hexagonal close-packed
|oxidation states='''0'''
|oxidation states comment=
|electronegativity=no data
|number of ionization energies=2
|ionization energy 1=2372.3
|ionization energy 2=5250.5
|ionization energy 3=
|atomic radius=
|atomic radius calculated=
|covalent radius=28
|Van der Waals radius=140
|magnetic ordering=[[diamagnetic]]
|magnetic ordering ref=<ref>[http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elementmagn.pdf Magnetic susceptibility of the elements and inorganic compounds], in Handbook of Chemistry and Physics 81st edition, CRC press.</ref>
|electrical resistivity=
|electrical resistivity at 0=
|electrical resistivity at 20=
|thermal conductivity=0.1513
|thermal conductivity 2=
|thermal diffusivity=
|thermal expansion=
|thermal expansion at 25=
|speed of sound=972
|speed of sound rod at 20=
|speed of sound rod at r.t.=
|Young's modulus=
|Shear modulus=
|Bulk modulus=
|Poisson ratio=
|Mohs hardness=
|Vickers hardness=
|Brinell hardness=
|CAS number=7440-59-7
|isotopes=
{{Infobox element/isotopes stable | mn=3 | sym=He | na=0.000137%* | n=1 | link=Helium-3 }}
{{Infobox element/isotopes stable | mn=4 | sym=He | na=99.999863%* | n=2 | link=Helium-4 }}
|isotopes comment=<nowiki>*</nowiki> Atmospheric value, abundance may differ elsewhere
|naming=after [[Helios]], Greek god of the Sun
|predicted by=
|prediction date=
|discovered by=[[Pierre Janssen]], [[Norman Lockyer]]
|discovery date=1868
|first isolation by=[[William Ramsay]], [[Per Teodor Cleve]], [[Abraham Langlet]]
|first isolation date=1895
}}<noinclude>
{{Template reference list}}
{documentation|1=Template:Infobox element/doc}}
</noinclude>