He - Helium

A light inert gas and the second most abundant element in the universe. Helium was discovered in 1868 by J. Norman Lockyear in the spectrum of a solar eclipse.

Atomic number - 2 Density g/mL 0 .00001787

Atomic weight u 4 .0026 Melting point K 0 .95

Bonding radius A 0 .93 Boiling point K 4 .215

Atomic radius A 0 .49 Heat of vaporization kJ/mol 0 .0845

Ionization Potential V 24 .587 Heat of fusion kJ/mol -

Electronegativity - - Specific heat J/gK 5 .193

The oxide is unknown.
Crystal are hexagonal.

Electron config. : 1s²

Isotopes of He: Click mass number for decay process, product for element page.

003 0.000137%

Stable

3.0160293 004 99.999863%

Stable

4.0026032 005
0.60 MeV
a/n,2.980 MeV
n/He-4
5.0122276 006
806.7 msec
B-,3.508 MeV
Li-6
6.0188880 007
160KEV
n,1.372 MeV
He-6
7.0280302 008
119.0 msec
B-/B-n,10.653
Li-8/Li-7
8.0339218 009
0.3 MeV
n,1.150 MeV
He-8
9.0438220

010
0.3 MeV
n,16.775 MeV
He-9
10.052399 MASS abund.
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass

Atomic number	-	2		Density	g/mL	0	.00001787
Atomic weight	u	4	.0026	Melting point	K	0	.95
Bonding radius	A	0	.93	Boiling point	K	4	.215
Atomic radius	A	0	.49	Heat of vaporization	kJ/mol	0	.0845
Ionization Potential	V	24	.587	Heat of fusion	kJ/mol	-
Electronegativity	-	-		Specific heat	J/gK	5	.193
The oxide is unknown.				Crystal are hexagonal.
Electron config. : 1s²

003 0.000137% Stable 3.0160293	004 99.999863% Stable 4.0026032	005 0.60 MeV a/n,2.980 MeV n/He-4 5.0122276	006 806.7 msec B-,3.508 MeV Li-6 6.0188880	007 160KEV n,1.372 MeV He-6 7.0280302	008 119.0 msec B-/B-n,10.653 Li-8/Li-7 8.0339218	009 0.3 MeV n,1.150 MeV He-8 9.0438220
010 0.3 MeV n,16.775 MeV He-9 10.052399	MASS abund. Halflife Particle, Energy Decay Product(s) Isotopic Mass