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| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | R | S | T | U | V | X | Z | ||
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| Helium | Hélium | Helij | Elio | Helium | ||||||||||||||||||||
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He Helium |
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- Helium was discovered by Pierre Jules César Janssen (France) and Sir William Ramsay (Scotland) in 1868. The origin of the name comes from the Greek word helios meaning sun. It is light, odourless, colourless inert gas. Second most abundant element in the universe.
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NOBLE GASES | |
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| Relative atomic mass: | 4.002602(2) | Electronic configuration: | 1s2 |
| Formal oxidation number: | 0 | Electronegativities: | - |
| Thermal conductivity: | 0.155 W m-1 K-1 | Electrical resistivity (20 °C): | - μΩcm |
| Atomic radius: | 128 pm | Standard state (20 °C): | gas |
| Density (g dm-3): | ~1760 (solid, pressure 6.9 MPa) 124.8 (liquid, m.p.) 0.1785 (gas, 273 K) |
Molar volume (cm3 mol-1): | ~2.27 (solid, pressure 6,9 MPa) 32.07 (liquid, m.p.) 22423.54 (gas, 273 K) |
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THERMAL PROPERTIES | |
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| Melting point: | -272.2 °C | Heat of fusion: | 0.021 kJ mol-1 |
| Boiling point: | -268.93 °C | Heat of vaporization: | 0.082 kJ mol-1 |
| Critical temperature: | -267.97 °C | Heat of atomization: | 0 kJ mol-1 |
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IONIZATION ENERGIES AND ABUNDANCE | |
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| 1st ionization energy: | 2372.34 kJ mol-1 | Abundance of element (air): | 5.2 ppm |
| 2nd ionization energy: | 5250.56 kJ mol-1 | Abundance of element (Earth's crust): | 0.008 ppm |
| 3rd ionization energy: | - kJ mol-1 | Abundance of element (oceans): | 0.0000072 ppm |
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ISOTOPES | |
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Isotopes | Relative atomic mass | Abundance (%) |
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3He | 3.016029310(1) | 0.000137(3) |
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4He | 4.002603250(1) | 99.999863(3) |
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MINERALS AND USES | |
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- Helium is found in natural gas deposits from wells in Texas, Oklahoma and Kansas. Used in balloons, deep sea diving and welding. Also used in very low temperature research. The price of 99.999 % pure helium gas costs 177.10 €/dm3 in small quantities (1 dm3) and about 2.52 €/dm3 in large quantities (300 dm3).
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REDUCTION POTENTIALS | |
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Balanced half-reaction | Eo / V | Annotation |
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