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Helium
Chemical Properties & Compounds
| Symbol | Atomic Number | Atomic Weight | Melting Point | Boiling Point | Phase | Density | Classification |
| He | 2 | 4.002602 | -272.2 °C | -268.93 °C | Gas | 0.1786 g/L | Noble Gas |
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|
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| General |
| Name, symbol, number |
helium, He, 2 |
| Chemical series |
noble gases |
| Group, period, block |
18, 1, s |
| Appearance |
colorless
 |
| Standard atomic weight |
4.002602(2) g·mol−1 |
| Electron configuration |
1s2 |
| Electrons per shell |
2 |
| Physical properties |
| Phase |
gas |
| Density |
(0 °C, 101.325 kPa)
0.1786 g/L |
| Melting point |
(at 2.5 MPa) 0.95 K
(−272.2 °C, −458.0 °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 |
| Heat capacity |
(25 °C) 20.786 J·mol−1·K−1 |
|
|
| Atomic properties |
| Crystal structure |
hexagonal close-packed |
| Electronegativity |
no data (Pauling scale) |
| Ionization energies |
1st: 2372.3 kJ/mol |
| 2nd: 5250.5 kJ/mol |
| Atomic radius (calc.) |
31 pm |
| Covalent radius |
32 pm |
| Van der Waals radius |
140 pm |
| Miscellaneous |
| Thermal conductivity |
(300 K) 151.3 m W·m−1·K−1 |
| CAS registry number |
7440-59-7 |
| Selected isotopes |
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|
| References |
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Helium Compounds
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Source: Wikipedia article Helium
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Chemistry Quick Facts
