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About Hydrogen

Hydrogen Bohr

Hydrogen, consisting of one proton and one electron, is the most basic and abundant element in the universe and the third most abundant (next to oxygen and silicon) on planet Earth. In fact, about 15% of all atoms on Earth are hydrogen atoms. Hydrogen is the lightest element, though accounts for roughly 90% of the universe by weight. When hydrogen burns in air, water is left as the only waste product. This element has long been theorized to have the ability of supplanting energy demands in Earth’s current fossil fuel economy. Despite hydrogen’s universal abundance, the easiest method of extraction on Earth is stream reforming of natural gas or through electrolysis of water. To this day, it is still not economically viable to produce hydrogen as an energy source in this manner due to its high input cost and relatively low resultant benefit.

The history of hydrogen’s discovery is a long one, with many ‘discoverers’ suggesting rightful claim. Robert Boyle, an English chemist and physicist, was probably the first to isolate the element in 1671 – though nothing was known about the concept of ‘elements’ at the time. Henry Cavendish, another English chemist and physicist, was able to accurately describe hydrogen’s properties by 1766. But it wasn’t until 1807 when John Dalton wrote about his ‘theory of atoms’ that the concept of ‘distinguishable elements’ was born. In the end, it is Cavendish who is generally credited with the discovery of hydrogen.

Raw hydrogen is primarily employed near the site where it is produced. The two largest uses of hydrogen include fossil fuel processing and ammonia production for fertilizer. Gaseous hydrogen has been used as a basis for lighter-than-air transportation. Many laboratory and common household acids and alcohols are composed of hydrogen compounds. Liquid hydrogen can be used as a superconductor, and when combined with liquid oxygen, is a main component of rocket fuel. Hydrogenation of unsaturated oils produces fats for consumable products. The list of applications that hydrogen touches are innumerable.

Many experts believe that hydrogen forms more compounds than any other element, as it readily attaches to many other elements. To summarize the various compounds with applications in industry and the commercial realm without being exhaustive would be rather incomprehensive. Three isotopes of hydrogen are known to exist, the most common being the single proton of 1H, or protium, which can be considered the essential building block of the universe. The addition to protium of one neutron yields another less common form of 2H, Hydrogen-2, known as deuterium (D). Deuterium is a naturally ocurring component of the earth's oceans; water artificially enriched with deuterium is known as "heavy water." While both protium and deuterium are stable isotopes, 3H (tritium) is radioactive and is often used as a tracer in scientific and industrial systems, in that it can easily be detected when as it gives off radiation. Large quantities of tritium are produced in and for laboratory settings.

Hydrogen Properties

Hydrogen Bohr ModelHydrogen is a Block S, Group 1, Period 1 element. The number of electrons in each of Hydrogen's shells is 1 and its electronic configuration is 1s1. The hydrogen atom has a radius of and it's Van der Waals radius is In its elemental form, CAS 1333-74-0, hydrogen is a colorless, tasteless, odorless, non-metallic, non-toxic, combustible gas. Hydrogen was discovered by Sir Henry Cavendish in 1766.

Symbol: H
Atomic Number: 1
Atomic Weight: 1.00794
Element Category: nonmetal
Group, Period, Block: 1, 1, s
Color: Colorless
Other Names: Dihydrogen
Melting Point: -259.14 °C, -434.45 °F, 14.01 K
Boiling Point: -252.87 °C, -423.17 °F, 20.28 K
Density: (0 °C, 101.325 kPa 0.08988 g/L
Liquid Density @ Melting Point: 0.07 (0.0763 solid) g·cm3
Density @ 20°C: 0.0000899 g/cm3
Density of Solid: 88 kgµm-3
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: 13.8033 K, 7.041 kPa
Critical Point: 32.938 K, 1.2858 MPa
Heat of Fusion (kJ·mol-1): 0.12
Heat of Vaporization (kJ·mol-1): 0.46
Heat of Atomization (kJ·mol-1): 216.003
Thermal Conductivity: 0.1805 W·m-1·K-1
Thermal Expansion: N/A
Electrical Resistivity: N/A
Tensile Strength: N/A
Molar Heat Capacity: (H2) 28.836 J·mol-1·K-1
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: (gas, 27 °C) 1310 m·s-1
Pauling Electronegativity: 2.2
Sanderson Electronegativity: 2.59
Allred Rochow Electronegativity: 2.2
Mulliken-Jaffe Electronegativity: 2.25 (s orbital)
Allen Electronegativity: 2.3
Pauling Electropositivity: 1.8
Reflectivity (%): N/A
Refractive Index: 1.000132 (gas; liquid 1.12) 
Electrons: 1
Protons: 1
Neutrons: 0
Electron Configuration: 1s1
Atomic Radius: N/A
Atomic Radius,
non-bonded (Å):
Covalent Radius: 31±5 pm
Covalent Radius (Å): 0.32
Van der Waals Radius: 120 pm
Oxidation States: 1, -1 (amphoteric oxide)
Phase: Gas
Crystal Structure: hexagonal
Magnetic Ordering: diamagnetic
Electron Affinity (kJ·mol-1) 72.743
1st Ionization Energy: 1312.0 kJ·mol-1
2nd Ionization Energy: N/A
3rd Ionization Energy: N/A
CAS Number: 1333-74-0
EC Number: 215-605-7
MDL Number: MFCD00070838
Beilstein Number: N/A
SMILES Identifier: [H]
InChI Identifier: InChI=1S/H
PubChem CID: 783
ChemSpider ID: 4515072
Earth - Total: 33 ppm 
Mercury - Total: 0.4 ppm
Venus - Total: 35 ppm
Earth - Seawater (Oceans), ppb by weight: 1.08E+08
Earth - Seawater (Oceans), ppb by atoms: 6.62E+08
Earth -  Crust (Crustal Rocks), ppb by weight: 1500000
Earth -  Crust (Crustal Rocks), ppb by atoms: 31000000
Sun - Total, ppb by weight: 7.5E+08
Sun - Total, ppb by atoms: 9.3E+08
Stream, ppb by weight: 1.15E+08
Stream, ppb by atoms: 1.1E+08
Meterorite (Carbonaceous), ppb by weight: 24000000
Meterorite (Carbonaceous), ppb by atoms: 1.7E+08
Typical Human Body, ppb by weight: 1E+08
Typical Human Body, ppb by atom: 6.2E+08
Universe, ppb by weight: 7.5E+08
Universe, ppb by atom: 9.3E+08
Discovered By: Henry Cavendish
Discovery Date: 1766
First Isolation: N/A

Health, Safety & Transportation Information for Hydrogen

Hydrogen (H) atomic and molecular weight, atomic number and elemental symbolHydrogen is the first and lightest element on the periodic table and the most abundant element in the universe. As a readily refinable gas that is lighter than air, its first uses were in ballooning experiments. It was the gas used by the famous Hindenburg dirigible. It now has numerous industrial applications in oil cracking and production of other non-metallic cations, such as ammonium compounds. Deuterium (2H), an isotope of hydrogen, is used to produce heavy water (2H2O) which has application in nuclear energy production. Hydrogen can easily be generated from renewable energy sources making it a primary focus in the area of alternative energy research. Hydrogen is nonpolluting and forms water as a harmless byproduct during use. The challenges associated with the use of hydrogen as a form of energy include developing safe, compact, reliable, and cost-effective hydrogen storage and delivery technologies.

Hydrogen is highly flammable. Safety data for Hydrogen and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the safety data tab. The below information applies to elemental (metallic) Hydrogen.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H220
Hazard Codes F+
Risk Codes 12
Safety Precautions 9-16-33
RTECS Number MW8900000
Transport Information UN 1049 2.1
WGK Germany nwg
Globally Harmonized System of
Classification and Labelling (GHS)
Flame-Flammables Gas Cylinder - Gases Under Pressure

Hydrogen Isotopes

Hydrogen (H) has three naturally occurring isotopes, 1H, 2H, and 3H.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
1H (protium) 1.00782503207(10) STABLE - 1/2+ 2.7928456 N/A 99.9885
2H (deuterium) 2.0141017778(4) STABLE - 1+ 0.8574376 1.9 0.0115
3H (tritium) 3.0160492777(25) 12.32(2) y β- to 3He 1/2+ 2.97896 8.21 -
4H 4.02781(11) 1.39(10)E-22 s [4.6(9) ] n to 3H 2- N/A 5.29 -
5H 5.03531(11) >9.1E-22 s ? 2n to 3H (1/2+) N/A 6.38 -
6H 6.04494(28) 2.90(70)E-22 s [1.6(4) ] 4n to 2H 2-# N/A 5.52 -
7H 7.05275(108)# 2.3(6)E-23# s [20(5)# ] 4n to 3H 1/2+# N/A 6.33 -
Hydrogen Elemental Symbol (H)

Recent Research & Development for Hydrogen

  • Bosun Jang, Taek Hyun Oh, Sejin Kwon, Effect of heat treatment of electrodes on direct borohydride-hydrogen peroxide fuel cell performance, Journal of Power Sources, Volume 268, 5 December 2014
  • Sheng-Yu Fang, Rong-Hsin Huang, Lay Gaik Teoh, Kan-Lin Hsueh, Wen-Kai Chao, Du-Cheng Tsai, Tse-Ning Yang, Fuh-Sheng Shieu, Coating TiVCr hydrogen storage alloy on the anode gas diffusion layer of proton exchange membrane fuel cells to improve performance, Journal of Power Sources, Volume 268, 5 December 2014
  • Qiong Cai, Claire S. Adjiman, Nigel P. Brandon, Optimal control strategies for hydrogen production when coupling solid oxide electrolysers with intermittent renewable energies, Journal of Power Sources, Volume 268, 5 December 2014
  • Lijie Zhang, Ming Meng, Xiaojing Wang, Shuang Zhou, Lijuan Yang, Tianyong Zhang, Lirong Zheng, Jing Zhang, Tiandou Hu, A series of copper-free ternary oxide catalysts ZnAlCex used for hydrogen production via dimethyl ether steam reforming, Journal of Power Sources, Volume 268, 5 December 2014
  • M.A. Deyab, Hydrogen generation by tin corrosion in lactic acid solution promoted by sodium perchlorate, Journal of Power Sources, Volume 268, 5 December 2014
  • Xiao-Qing Bao, Lifeng Liu, Improved photo-stability of silicon nanobelt arrays by atomic layer deposition for efficient photocatalytic hydrogen evolution, Journal of Power Sources, Volume 268, 5 December 2014
  • Yi Yu, Xiaolin Shu, Yi-Nan Liu, Guang-Hong Lu, Molecular dynamics simulation of hydrogen dissolution and diffusion in a tungsten grain boundary, Journal of Nuclear Materials, Volume 455, Issues 1–3, December 2014
  • Mancun Song, Pucheng Pei, Hongshan Zha, Huachi Xu, Water management of proton exchange membrane fuel cell based on control of hydrogen pressure drop, Journal of Power Sources, Volume 267, 1 December 2014
  • Fakhteh Siavashi, Majid Saidi, Mohammad Reza Rahimpour, Purge gas recovery of ammonia synthesis plant by integrated configuration of catalytic hydrogen-permselective membrane reactor and solid oxide fuel cell as a novel technology, Journal of Power Sources, Volume 267, 1 December 2014
  • Si-yao Guo, Song Han, Constructing a novel hierarchical 3D flower-like nano/micro titanium phosphate with efficient hydrogen evolution from water splitting, Journal of Power Sources, Volume 267, 1 December 2014
  • Tong Liu, Chunguang Chen, Fan Wang, Xingguo Li, Enhanced hydrogen storage properties of magnesium by the synergic catalytic effect of TiH1.971 and TiH1.5 nanoparticles at room temperature, Journal of Power Sources, Volume 267, 1 December 2014
  • Tong Liu, Yurong Cao, Hui Li, Wusheng Chou, Xingguo Li, Superior hydrogen storage and electrochemical properties of Mg–La–Pd trilayer films at room temperature, Journal of Power Sources, Volume 267, 1 December 2014
  • Julián Puszkiel, Fabiana C. Gennari, Pierre Arneodo Larochette, Horacio E. Troiani, Fahim Karimi, Claudio Pistidda, Rapee Gosalawit–Utke, Julian Jepsen, Torben R. Jensen, Carsten Gundlach, Martin Tolkiehn, José Bellosta von Colbe, Thomas Klassen, Martin Dornheim, Hydrogen storage in Mg–LiBH4 composites catalyzed by FeF3, Journal of Power Sources, Volume 267, 1 December 2014
  • Damien Connétable, Yu Wang, Döme Tanguy, Segregation of hydrogen to defects in nickel using first-principles calculations: The case of self-interstitials and cavities, Journal of Alloys and Compounds, Volume 614, 25 November 2014
  • Satoshi Akamaru, Masanori Hara, Masao Matsuyama, Alloying effects on the hydrogen-storage capability of Pd–TM–H (TM = Cu, Au, Pt, Ir) systems, Journal of Alloys and Compounds, Volume 614, 25 November 2014
  • M.G. Verón, F.C. Gennari, Thermodynamic behavior of the Mg–Co–H system: The effect of hydrogen cycling, Journal of Alloys and Compounds, Volume 614, 25 November 2014
  • A.V. Vyvodtceva, M.G. Shelyapina, A.F. Privalov, Yu.S. Chernyshev, D. Fruchart, 1H NMR study of hydrogen self-diffusion in ternary Ti–V–Cr alloys, Journal of Alloys and Compounds, Volume 614, 25 November 2014
  • Bao Zhang, Ying Wu, Effects of additives on the microstructure and hydrogen storage properties of the Li3N–MgH2 mixture, Journal of Alloys and Compounds, Volume 613, 15 November 2014
  • M.A. McArthur, L. Jorge, S. Coulombe, S. Omanovic, Synthesis and characterization of 3D Ni nanoparticle/carbon nanotube cathodes for hydrogen evolution in alkaline electrolyte, Journal of Power Sources, Volume 266, 15 November 2014
  • Sujuan Hu, Lichao Jia, Bo Chi, Jian Pu, Li Jian, Visible light driven (Fe, Cr)-codoped La2Ti2O7 photocatalyst for efficient photocatalytic hydrogen production, Journal of Power Sources, Volume 266, 15 November 2014