Helyo

Helium
2He
- ↑ He ↓ Ne Periodic table hydrogen ← helium → lithium
Appearance
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	18, 1, s
Standard atomic weight	4.002602(2)
Electron configuration	1s2 2
History
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
Miscellanea
Crystal structure	hexagonal close-packed
Magnetic ordering	diamagnetic
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.

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.

Galeriya sa hulagway

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