Purple glow in its plasma state
|Standard atomic weight (Ar, standard)||[1.00784, 1.00811] conventional: 1.008|
|Hydrogen in the periodic table|
|Atomic number (Z)||1|
|Element category||reactive nonmetal|
Electrons per shell
|Phase at STP||gas|
|Melting point||13.99 K (−259.16 °C, −434.49 °F)|
|Boiling point||20.271 K (−252.879 °C, −423.182 °F)|
|Density (at STP)||0.08988 g/L|
|when liquid (at m.p.)||0.07 g/cm3 (solid: 0.0763 g/cm3)|
|when liquid (at b.p.)||0.07099 g/cm3|
|Triple point||13.8033 K, 7.041 kPa|
|Critical point||32.938 K, 1.2858 MPa|
|Heat of fusion||(H2) 0.117 kJ/mol|
|Heat of vaporization||(H2) 0.904 kJ/mol|
|Molar heat capacity||(H2) 28.836 J/(mol·K)|
|Oxidation states||−1, +1 (an amphoteric oxide)|
|Electronegativity||Pauling scale: 2.20|
|Covalent radius||31±5 pm|
|Van der Waals radius||120 pm|
|Spectral lines of hydrogen|
|Speed of sound||1310 m/s (gas, 27 °C)|
|Thermal conductivity||0.1805 W/(m·K)|
|Magnetic susceptibility||−3.98·10−6 cm3/mol (298 K)|
|CAS Number||12385-13-6 |
|Discovery||Henry Cavendish (1766)|
|Named by||Antoine Lavoisier (1783)|
|Main isotopes of hydrogen|
Hydrogen is the chemical element with the symbol H and atomic number 1. It has a standard atomic weight of 1.008, meaning it is the lightest element in the periodic table. Hydrogen is the most common chemical element in the Universe, with 75% of all baryonic mass being hydrogen. Stars are made up of mostly hydrogen. Hydrogen's most common isotope has one proton with one electron orbiting around it.
Hydrogen in nature[change | change source]
In its pure form on Earth, hydrogen is usually a gas. Hydrogen is also one of the parts that make up a water molecule. Hydrogen is important because it is the fuel that powers the Sun and other stars. Hydrogen makes up about 74% of the entire universe. Hydrogen's symbol on the Periodic Table of Elements is H.
Pure hydrogen is normally made of two hydrogen atoms connected together. Scientists call these diatomic molecules. Hydrogen will have a chemical reaction when mixed with most other elements. It has no color or smell.
Pure hydrogen is very uncommon in the Earth's atmosphere. In nature, it is usually in water. Hydrogen is also in all living things, as a part of the organic compounds that living things are made of. In addition, hydrogen atoms can combine with carbon atoms to form hydrocarbons. Petroleum and other fossil fuels are made of these hydrocarbons and commonly used to create energy for human use.
Hydrogen has three isotopes; the others are called deuterium and tritium. Like regular hydrogen, they both have only one proton and one electron, but deuterium also has one neutron and tritium has two. These other types of hydrogen are important in nuclear energy and organic chemistry reactions.
Some other facts about hydrogen:
- It is a gas at room temperature
- It acts like a metal when it is solid.
- It is the lightest element in the Universe.
- It is the most common element in the Universe.
- It burns or explodes when it touches a flame.
- glows purple when it is in plasma state.
History of Hydrogen[change | change source]
Hydrogen was first separated in 1671 by Robert Boyle. Henry Cavendish in 1776 identified it as a distinct element and discovered that burning it made water.
Uses of Hydrogen[change | change source]
The main uses are in the petroleum industry and in making ammonia by the Haber process. Some is used elsewhere in the chemical industry. A little of it is used as fuel, for example in rockets for spacecraft. Most of the hydrogen that people use comes from a chemical reaction between natural gas and steam.
Nuclear fusion[change | change source]
Nuclear fusion is a very powerful source of energy. It relies on forcing atoms together to make helium and energy, exactly as happens in a star like the Sun, or in a hydrogen bomb. This needs a large amount of energy to get started, and is not easy to do yet. A big advantage over nuclear fission, which is used in today's nuclear power stations, is that it makes less nuclear waste and does not use a toxic and rare fuel like uranium. More than 600 million tons of hydrogen undergo fusion every second on the Sun.
Burning Hydrogen[change | change source]
The electrolysis of water breaks water into hydrogen and oxygen, using electricity. Burning hydrogen combines with oxygen molecules to make steam (pure water vapor). A fuel cell combines hydrogen with an oxygen molecule, releasing an electron as electricity. For these reasons, many people believe hydrogen power will eventually replace other synthetic fuels.
Hydrogen can also be used as fuel in a fuel cell, or burned to make heat for steam turbines or internal combustion engines. Hydrogen can be created from many sources such as coal, natural gas or electricity, and therefore represents a valuable addition to the power grid; in the same role as natural gas. Such a grid and infrastructure with fuel cell vehicles is now planned by a number of countries including Japan, Korea and many European countries. This allows these countries to buy less petroleum, which is an economic advantage. The other advantage is that used in a fuel cell or burned in a combustion engine as in a hydrogen car, the motor does not make pollution. Only water, and a small amount of nitrogen oxides, forms.
References[change | change source]
- Wiberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001). Inorganic chemistry. Academic Press. p. 240. ISBN 978-0123526519.
- Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 978-0-8493-0486-6.
- Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 978-0-8493-0464-4.
- "Hydrogen". Van Nostrand's Encyclopedia of Chemistry. Wylie-Interscience. 2005. pp. 797–799. ISBN 978-0-471-61525-5.
- Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 183–191. ISBN 978-0-19-850341-5.
- Stwertka, Albert (1996). A Guide to the Elements. Oxford University Press. pp. 16–21. ISBN 978-0-19-508083-4.
- Cain, Fraser, Universe Today (November 7, 2016). "When was the first light in the universe?". Phys.org. Retrieved 29 November 2016.
- EIA.doe.gov - What is Hydrogen?
- "The magic of syngas". chemrec.se. 2012. Retrieved 7 March 2012.
- "What is Fusion?". iter.org. ITER Organization. 2012. Retrieved 7 March 2012.
- "NASA's Cosmicopia". NASA. Retrieved 28 February 2013.
Other websites[change | change source]
- Hydrogen -Citizendium