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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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| Hydrogen | Hydrogène | Vodik | Idrogeno | Wasserstoff | ||||||||||||||||||||
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H Hydrogenium |
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- Hydrogen was discovered by Sir Henry Cavendish (England) in 1766. The origin of the name comes from the Greek words hydro and genes meaning water and generate. It is colourless, odourless gas, burns and forms explosive mixtures in air. Reacts violently with oxidants. Hydrogen is the most abundant element in the universe.
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| Relative atomic mass: | 1.00794(7) | Electronic configuration: | 1s1 |
| Formal oxidation number: | -1 +1 | Electronegativities: | 2.2 |
| Thermal conductivity: | 0.183 W m-1 K-1 | Electrical resistivity (20 °C): | - μΩcm |
| Atomic radius: | 37.3 pm | Standard state (20 °C): | gas |
| Density (g dm-3): | 76.0 (solid, 11 K) 70.8 (liquid, b.p.) 0.08988 (gas, 273 K) |
Molar volume (cm3 mol-1): | 13.26 (solid, 11 K) 14.24 (liquid, b.p.) 22423.54 (gas, 273 K) |
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THERMAL PROPERTIES | |
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| Melting point: | -259.34 °C | Heat of fusion: | 0.12 kJ mol-1 |
| Boiling point: | -252.87 °C | Heat of vaporization: | 0.46 kJ mol-1 |
| Critical temperature: | -239.96 °C | Heat of atomization: | 216.003 kJ mol-1 |
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IONIZATION ENERGIES AND ABUNDANCE | |
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| 1st ionization energy: | 1312.06 kJ mol-1 | Abundance of element (air): | 0.53 ppm |
| 2nd ionization energy: | - kJ mol-1 | Abundance of element (Earth's crust): | 1400 ppm |
| 3rd ionization energy: | - kJ mol-1 | Abundance of element (oceans): | (H2O) ppm |
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ISOTOPES | |
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Isotopes | Relative atomic mass | Abundance (%) |
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1H | 1.007825032(1) | 99.985(1) |
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2H | 2.014101778(1) | 0.015(1) |
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3H | 3.016049268(1) | * |
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MINERALS AND USES | |
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- Commercial quantities of hydrogen are produced by reacting superheated steam with methane or carbon. In lab work from reaction of metals with acid solutions or electrolysis. Most hydrogen is used in the production of ammonia and in metal refining. Also used as fuel in rockets. Its two heavier isotopes (deuterium and tritium) used respectively for nuclear fusion. The price of 99.999 % pure hydrogen gas costs 200.70 €/dm3 in small quantities (1 dm3) and about 2.21 €/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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2H+ + 2e-  H2(g) |
±0.000 | |
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2H+ + 2e- H2(g) |
- 0.41 | [H+] = 10-7 mol dm-3 |
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2H+ + 2e- H2(g) |
- 0.005 | 1 mol dm-3 HCl |
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2H+ + 2e- H2(g) |
- 0.005 | 1 mol dm-3 HClO4 |
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2H2O + 2e- H2(g) + 2OH- |
- 0.83 | |
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H2O2 + 2H+ + 2e- 2H2O |
+1.77 | |
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HO2- + H2O + 2e- 3OH- |
+0.88 | |
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H2(g) + 2e- 2H- |
- 2.25 | |
