|
Historical, sociological, institutional, and cultural aspects of hydrogen chemistry will be included here. Particular individuals and groups associated with hydrogen will also be mentioned. Information about its biological, geological, and astronomical abundances can be considered. Hydrogen chemistry includes information about its chemical properties, bulk and molecular forms, atomic properties, and isotopes. |
|
Hydrogen is a component of most organic compounds and is essential to life as we know it. It is usually found in combined form, rarely as the free element.
Hydrogen is usually found in combined form, rarely as the free element. The geological history of hydrogen is uncertain. It is thought to have been more abundant early in the earth's history, but earth is not massive enough to retain large amounts of hydrogen over geological time periods, and much of it is believed to have escaped. It is not evenly distributed over the earth's surface. There are trace amounts in the lower atmosphere, although the proportion increases until it is the predominant gas of the upper atmosphere. Most of the earth's supply is found in the hydrosphere, combined with oxygen in the form of water. Hydrogen is found in minimal amounts in the crust.
Hydrogen is the most abundant element in the universe, and is thought to have been present since its origin. It is present in all observed galaxies, stars and in many planets of the solar system.
Hydrogen is present in many organic systems and inorganic systems.
Compounds
Hydrogen is known to form a compound magnesium hydride, MgH2, but this reacts so easily with oxygen and water that it is difficult to study.
Hydrogen is present in most of the enormous class of organic compounds including the hydrocarbon compounds. These include methane, CH4 and formaldehyde H2CO.
Hydroge is known to form silanes, somewhat analogous to the hydrocarbons, beginning with SiH4, but most of these react so readily with free oxygen and water that they are difficult to study.
Hydrogen reacts with nitrogen to form ammonia, NH3
Hydrogen reacts with oxygen to form water, H20, and hydrogen peroxide, H202
Hydrogen reacts with sulfur to form hydrogen sulfide, H2S.
Hydrogen exists at standard temperatures and pressures as the diatomic gas. At high temperatures it disassociates to form atomic hydrogen, and at still higher temperatures ionizes to nuclei, (principally protons) and electrons.
Hydrogen nuclei may react with each other in a process called fusion, which forms higher isotopes of hydrogen and helium
Under standard conditions of temperature and pressure, hydrogen exists as the diatomic gas, H2. It is only found in the liquid form at extremely cold temperatures, and in the solid form at even colder temperatures.
Isotopes
| Nuclear composition | Name | Mass | Abundance | |
| 11H | Protium | 1.007825032(1) | 99.985% | |
| 21H | Deuterium | 2.014101778(1) | 0.015% | |
| 31H | Tritium | 3.016049268(1) | Trace |
Hydrogen has a melting/freezing point of 14.01 K, -259.14 °C, -434.45 °F
Hydrogen has a boiling/condensation point of 20.28 K, -252.87 °C, -423.17 °F