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He
in WebElements
in X-Ray info
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He, 2
helium (English)
hélium, m. (French)
Helium, n. (German)
gelij (Russian)
helio (Spanish)
helium (Swedish)
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| Symbol, number | He, 2 (noble gas), Group: 18; 8A |
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| Weight | 4.002602 |
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| In Nature | |
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| Discovered | 1895, by William Ramsay, William Crookes, P.T. Cleve and N.A. Langlet (England, Sweden) |
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| Density [kg/m3] | 124.8 [4.2 K] (liquid) 0.1785 [273 K] (gas) |
| Molar volume | 32.07 [4 K] cm3 |
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| Melting Temperature | 0.95 K (-272.05 °C) Enthalpy: 4.216 kJ/mol |
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| Boiling Temperature | 4.216 K (-268.784 °C) Enthalpy: 0.082 kJ/mol |
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| Thermal | Conductivity: 0.152 [300 K] (gas) W/Km |
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| Configuration | 1s2 2s1 |
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| Ionisation [kJ/mol] |
| M--> |
M+--> |
M2+--> |
M3+--> |
M4+--> |
M5+--> |
M6+--> |
M7+--> |
M8+--> |
M9+-->M10+ |
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| Thermodynamics |
| State |
DfH° |
DfG° |
S° |
CpH |
H°298.15-H°0 |
| [kJ/mol] |
[J/Kmol] |
[kJ/mol] |
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| Isotopes |
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Mass |
In nature |
Half-life |
Spin |
m/mN |
NMM |
Decay |
| 3He |
3.01602931 |
0.000137% |
stable |
1/2 |
-2.127624 |
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| 4He |
4.00260324 |
99.999863% |
stable |
0 |
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| 6He |
6.018886 |
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0.807 s |
3/2 |
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β- to 6Li |
| 8He |
8.03392 |
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0.119 s |
3/2 |
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β- to 8Li; β-+n to 7Li |
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