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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

  • Role of hydrogen sulfide within the dorsal motor nucleus of the vagus in the control of gastric function in rats. Sun HZ, Yu KH, Ai HB. Neurogastroenterol Motil. 2015 Mar 14.
  • Reactivity and Selectivity Patterns in Hydrogen Atom Transfer from Amino Acid C-H Bonds to the Cumyloxyl Radical. Polar Effects as a Rationale for the Preferential Reaction at Proline Residues. Salamone M, Basili F, Bietti M. J Org Chem. 2015 Mar 16.
  • A Ruthenium-Based Biomimetic Hydrogen Cluster for Efficient Photocatalytic Hydrogen Generation from Formic Acid. Chang CH, Chen MH, Du WS, Gliniak J, Lin JH, Wu HH, Chan HF, Yu JS, Wu TK. Chemistry. 2015 Mar 12.
  • Production of ready-to-eat lentil sprouts with improved antioxidant capacity: Optimization of elicitation conditions with hydrogen peroxide. ?wieca M. Food Chem. 2015 Aug 1
  • Nonclassical correlations between terahertz-bandwidth photons mediated by rotational quanta in hydrogen molecules. Bustard PJ, Erskine J, England DG, Nunn J, Hockett P, Lausten R, Spanner M, Sussman BJ. Opt Lett. 2015 Mar 15
  • Origin of the 900 cm(-1) broad double-hump OH vibrational feature of strongly hydrogen-bonded carboxylic acids. Van Hoozen BL Jr, Petersen PB. J Chem Phys. 2015 Mar 14
  • Generation of three-octave-spanning transient Raman comb in hydrogen-filled hollow-core PCF. Tani F, Belli F, Abdolvand A, Travers JC, Russell PS. Opt Lett. 2015 Mar 15
  • Thrombin or Ca++-Ionophore-Mediated Fall in Endothelial ATP Levels Independent of Poly(ADP-Ribose) Polymerase Activity and NAD Levels - Comparison with the Effects of Hydrogen Peroxide. Halldórsson H, Thors B, Thorgeirsson G. Nucleosides Nucleotides Nucleic Acids. 2015 Apr 3
  • On the mechanism of catalytic hydrogenation of thiophene on hydrogen tungsten bronze. Xi Y, Chen Z, Gan Wei Kiat V, Huang L, Cheng H. Phys Chem Chem Phys. 2015 Mar 16.
  • Snapshots of the Fluctuating Hydrogen Bond Network in Liquid Water on the Sub-Femtosecond Timescale with Vibrational Resonant Inelastic x-ray Scattering. Pietzsch A, Hennies F, Miedema PS, Kennedy B, Schlappa J, Schmitt T, Strocov VN, Föhlisch A. Phys Rev Lett. 2015 Feb 27
  • Correction to "Investigation of the Structure of Ethanol-Water Mixtures by Molecular Dynamics Simulation I: Analyses Concerning the Hydrogen-Bonded Pairs". Gereben O, Pusztai L. J Phys Chem B. 2015 Mar 13.
  • From hydrogen bonding to metal coordination and back: Porphyrin-based networks on Ag(111). Studener F, Müller K, Marets N, Bulach V, Hosseini MW, Stöhr M. J Chem Phys. 2015 Mar 14
  • Thermodynamically neutral Kubas-type hydrogen storage using amorphous Cr(iii) alkyl hydride gels. Morris L, Trudeau ML, Reed D, Book D, Antonelli DM. Phys Chem Chem Phys. 2015 Mar 13.
  • Endogenous Prostaglandins and Afferent Sensory Nerves in Gastroprotective Effect of Hydrogen Sulfide against Stress-Induced Gastric Lesions. Magierowski M, Jasnos K, Kwiecien S, Drozdowicz D, Surmiak M, Strzalka M, Ptak-Belowska A, Wallace JL, Brzozowski T. PLoS One. 2015 Mar 16
  • Matrix metalloproteinases in atherosclerosis: role of nitric oxide, hydrogen sulfide, homocysteine, and polymorphisms. Vacek TP, Rehman S, Neamtu D, Yu S, Givimani S, Tyagi SC. Vasc Health Risk Manag. 2015 Feb 27
  • Hydrogen sulphide regulates inward-rectifying K+ channels in conjunction with stomatal closure. Papanatsiou M, Scuffi D, Blatt MR, Garia-Mata C. Plant Physiol. 2015 Mar 13.
  • Hydrogen-bonded clusters of 1, 1'-ferrocenedicarboxylic acid on Au(111) are initially formed in solution. Quardokus RC, Wasio NA, Brown RD, Christie JA, Henderson KW, Forrest RP, Lent CS, Corcelli SA, Alex Kandel S. J Chem Phys. 2015 Mar 14
  • Role of hydrogen-bonding and its interplay with octahedral tilting in CH3NH3PbI3. Lee JH, Bristowe NC, Bristowe PD, Cheetham AK. Chem Commun (Camb). 2015 Mar 13.
  • Effects of Hydrogen Sulfide on Modulation of Theta-Gamma Coupling in Hippocampus in Vascular Dementia Rats. Xu X, Liu C, Li Z, Zhang T. Brain Topogr. 2015 Mar 14.
  • The relationship between the boron dipyrromethene (BODIPY) structure and the effectiveness of homogeneous and heterogeneous solar hydrogen-generating systems as well as DSSCs. Luo GG, Lu H, Zhang XL, Dai JC, Wu JH, Wu JJ. Phys Chem Chem Phys. 2015 Mar 16.