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colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field

Spectral lines of helium
General properties
Name, simbolo, kaiphan helium, He, 2
Pronunciation Plantilya:IPAc-en Plantilya:Respell
Element category gas nga halangdon
Group, period, block 181, s
Standard atomic weight 4.002602(2)
Electron configuration 1s2
Electron shells of helium (2)
Discovery Pierre Janssen, Norman Lockyer (1868)
First isolation William Ramsay, Per Teodor Cleve, Abraham Langlet (1895)
Physical properties
Phase gas
Density (0 °C, 101.325 kPa)
0.1786 g/L
Liquid density at m.p. 0.145 g·cm−3
Liquid density at b.p. 0.125 g·cm−3
Melting point (at 2.5 MPa) 0.95 K, −272.20 °C, −457.96 °F
Boiling point 4.22 K, −268.93 °C, −452.07 °F
Critical point 5.19 K, 0.227 MPa
Heat of fusion 0.0138 kJ·mol−1
Heat of vaporization 0.0829 kJ·mol−1
Molar heat capacity 5R/2 = 20.786 J·mol−1·K−1
Vapor pressure (defined by ITS-90)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K)     1.23 1.67 2.48 4.21
Atomic properties
Oxidation states 0
Electronegativity no data (Pauling scale)
Ionization energies 1st: 2372.3 kJ·mol−1
2nd: 5250.5 kJ·mol−1
Covalent radius 28 pm
Van der Waals radius 140 pm
Crystal structure hexagonal close-packed
Helium has a hexagonal close-packed crystal structure
Magnetic ordering diamagnetic[1]
Thermal conductivity 0.1513 W·m−1·K−1
Speed of sound 972 m·s−1
CAS registry number 7440-59-7
Most stable isotopes
Main article: Isotopes of helium
iso NA half-life DM DE (MeV) DP
3He 0.000137%* 3He is stable with 1 neutron
4He 99.999863%* 4He is stable with 2 neutrons
*Atmospheric value, abundance may differ elsewhere.
· r

Ang helyo (Iningles helium) mao ang elementong kimiko sa talaang peryodiko nga may simbolo nga He ug kaiphan nga atomik 2. Ang helyo mao ang gas nga halangdon.

Ang mga gi basihan niini[usba | edit source]

  1. Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.

Galeriya sa hulagway[usba | edit source]