Hydrogen is a chemical element with an atomic number of 1 in the periodic table. Occurring as a part of the H2O molecule, it’s the most plentiful element that occurs in the Universe. With 0.15 % concentration, it’s also the 10th most abundant chemical element in Earth’s crust. As a member of the hydrogen family of elements, this chemical substance that occurs both as a gas and a non-metal has only one valence electron.  


Fact Box

Chemical and Physical Properties of Hydrogen

The symbol in the periodic table of elements: (H)

Atomic number: 1

Atomic weight (mass): 1.008 g.mol-1

Group number: 1

Period: 1

Color: A colorless, non-metal substance

Physical state: Gas at room temperature

Half-life: From 10−21 second to 1034 years

Electronegativity according to Pauling: 2.1

Density: 0.000082 g.cm−3 at 20 °C

Melting point: −259.16°C, −434.49°F, 13.99 K

Boiling point: −252.879°C, −423.182°F, 20.271 K

Van der Waals radius: 0.12 nm

Ionic radius: 0.208 (-1) nm

Isotopes: 3

Most characteristic isotope: 1H, 2

Electronic shell: 1s1

The energy of the first ionization: 1311 kJ.mol-1

The energy of the second ionization: This element doesn’t have a second ionization

Discovery date: In 1818 by Henry Cavendish


Classified in the periodic table under the symbol (H), atomic number X, atomic mass of 1.008 g.mol-1, and electron configuration 1s1, hydrogen is a colorless and odorless gas with a diatomic molecule (H2). It reaches its boiling point at −252.879°C (−423.182°F, 20.271 K), while the melting point is achieved at X−259.16°C (−434.49°F, 13.99 K).

The lightest and the simplest element of all existing chemicals has an electronegativity of 2.1 according to Pauling, whereas the atomic radius according to van der Waals is 0.12 nm. 


Pure hydrogen burns violently with oxidants and forms explosive compounds when it comes to contact with air. When substantial pressure is applied, this non-metal substance changes its aggregate state into a liquid gas. Hydrogen is easily absorbed by metals, and it’s easily soluble in both organic solvents – even more so than in water. 



How Was Hydrogen Discovered?

The story on hydrogen does not begin at the date recognized as the official introduction of this chemical element in the world of science. Namely, two centuries before Henry Cavendish received accolades for his outstanding achievement, a few other scientists seem to have been on its trace.


Paracelsus and His Discovery of Hydrogen

At the beginning of the 1500s, the alchemist Paracelsus observed a flammable gas rising from the metal when he tried to treat it with diluted sulfuric acid. However, this gaseous by-product of his chemical attempt couldn’t be supported by further scientific evidence because Paracelsus firmly believed that there are only three primary chemical elements in the world that he called “the tria prima” – salt, sulfur, and mercury.

Upon his observance, the other chemicals were merely a combination of these three substances. Of course, the times of Paracelsus were the genesis of science, so he wasn’t able to conduct more thorough analyses of the new substance. 


Robert Boyle and Henry Cavendish’s Attempts to Isolate Hydrogen

Inspired by Paracelsus’ work, in 1670 the Anglo-Irish chemist, physicist, and inventor Robert Boyle (1627 – 1691) tried to reproduce the chemical trials of the alchemist. In his attempt, he only managed to demonstrate that hydrogen gas burns when it comes into contact with air, more precisely – with O2.


Henry Cavendish and His Discovery of Hydrogen

A century later, the English scientist and member of the Royal Society of London, Henry Cavendish (1731 – 1810) recognized the new element when he tried to make a chemical reaction between hydrochloric acid and zinc. Among all the properties of hydrogen he determined, Cavendish also discovered that the gaseous substance produces water when burned. Thus, he labeled the substance as ‘inflammable air’. 


Sir Humphry Davy’s Consecutive Research on Hydrogen

Being a master of electrolysis, Sir Humprey Davy attempted an experiment by conducting an electric current through purified water. The resulting outcome showed Davy that he could isolate all the elements from the observed compound by using electricity. 


With this particular experiment, Davy managed to isolate both hydrogen and oxygen from the water which led him to the belief that the elements were bound between each other by an electrical phenomenon. By this, Sir Humprey Davy succeeded in discovering the real nature of chemical bonding. 


How Did Hydrogen Get Its Name?

The French scientist Antoine Lavoisier (1743 – 1794) named the water-forming gas as hydrogen in 1783. The name of the element is a portmanteau from the Greek words hydro (water) and gen (birth; born; produced). 


Where Can You Find Hydrogen?

Hydrogen is the most abundant element that can be found in the Universe that mostly occurs in the form of a gaseous substance. While Jupiter is mostly made of hydrogen, this substance can also be found on Saturn, in the Sun, as well as in the composition of some stars. 


On Earth, though, hydrogen occurs in all waters as the H2O compound. However, due to its light atomic mass, hydrogen cannot be retained close to Earth, so it escapes into space by the force of our planet’s gravity


For commercial uses, the production of hydrogen is performed by heating natural gas with steam to form a mixture of hydrogen and carbon monoxide, labeled as syngas. The process continues by a separation of elements from the compound so that hydrogen is obtained.

The most abundant hydrogen isotope is protium, while tritium is the least abundant form of hydrogen. Each year, there are about 3 billion cubic feet of hydrogen produced in the United States. 


Hydrogen in Everyday Life

Element 1 has an enormous variety of uses in everyday life. Being part of the water molecule, it’s vital for all life forms on Earth. Simply put – there can’t be life without water. It’s also found in plenty of compounds that have found practical use in our living. Such are the following.


  • Hydrogen peroxide – used as an antiseptic in medicine, a mouth rinse and a bleaching agent in dentistry, as a disinfecting and brightening agent, in facial masks, etc. Namely, when hydrogen peroxide is applied to the skin or any other surface of the body, it releases oxygen that begins to foam. This chemical process cleans the area of application and removes the dead skin cells.  

How Dangerous Is Hydrogen?

Hydrogen gas is colorless and odorless, but extremely flammable. This presents a great danger of accidental fire and burns since the presence of this gas is not evident at first. For this purpose, gas detectors are used in the places where there is a risk of exposure to the elemental form of hydrogen, or to some of its toxic compounds. 


Exposure to high levels of hydrogen by inhalation can lead to loss of consciousness which may have fatal consequences. 


Environmental Effects of Hydrogen

This chemical element plays probably the most vital biological role. Since it forms the water molecule, it’s essential for the life of all live beings. However, when high concentrations of this gas are released in the atmosphere, the environment becomes deficient in oxygen which harms all forms of life in the environment, including people. 


Since most of the commercially used quantities of hydrogen are obtained from natural gas via processes that generate carbon dioxide (CO2), the search for alternative sources of fuel has been on the rise in recent years. 


The newly developed hydrogen fuel cell technology allows for obtaining alternative power sources of renewable energy. According to the BMW Corporation, the ecological vehicles on hydrogen fuel as a fossil fuel replacement in the eco-cars, i.e. electromobiles, emit fewer pollutants in the environment when burnt in the internal combustion engines.

Since hydrogen is an energy carrier with no carbon molecules attached to it, it produces only water when it burns which makes it also a more cost-effective solution. 


Isotopes of Hydrogen

The isotopes 1H, 2H, and 3H are the only naturally occurring forms of hydrogen. With a half-life of 12.32 years, the 3H is the least stable isotope among them. On the other hand, the most stable hydrogen isotope is the 5H form of this chemical element. The rest of the isotopes are synthetically produced isotopes with a heavier mass and a half-life of less than one zeptosecond (10−21 second).


Nuclide[8]ZNIsotopic mass (Da)[9]


[n 1]



[resonance width]




[n 2]




[n 3]

Spin and



[n 4][n 5]

Natural abundance (mole fraction)Note
Normal proportionRange of variation
1H101.00782503224(9)Stable[n 6][n 7]1/2+0.999885(70)0.999816–0.999974Protium
2H (D)[n 8][n 9]112.01410177811(12)Stable1+0.000115(70)[n 10]0.000026–0.000184Deuterium
3H (T)[n 11]123.01604928199(23)12.32(2) yβ3He1/2+Trace[n 12] Tritium
4H134.02643(11)1.39(10)×10−22 s


[3.28(23) MeV]

5H145.03531(10)> 9.1×10−22 s


[< 0.5 MeV]

6H156.04496(27)2.90(70)×10−22 s


[1.6(4) MeV]


Source: Wikipedia


List of Hydrogen Compounds

A large number of the compounds in which hydrogen participates with its atoms are easily found in nature and can be used by the industries with no prior processing or preparation. Such are ammonia (NH₃), methane (CH4), and hydrogen peroxide (H₂O₂). 


The most frequently occurring hydrogen compounds are in the form of oxides, hydrates, alkaloids, carbohydrates, ethers, salts, terpenes, organic polymers, organic compounds, and acids, but water (H2O) is by far the most significant compound the hydrogen participates in, among them all:


  • Accelerated hydrogen peroxide
  • Argon fluorohydride
  • Binary compounds of hydrogen
  • Bromic acid
  • Bromous acid
  • Carbonaceous sulfur hydride
  • Chloroplatinic acid
  • Chlorous acid
  • Chromic acid
  • Dioxidanylium
  • Disulfuric acid
  • Fluoronium
  • Fulminic acid
  • Helium hydride ion
  • Hexafluorosilicic acid
  • Hydrogen astatide
  • Hydrogen bromide
  • Hydrogen chalcogenide
  • Hydrogen chloride
  • Hydrogen cyanide
  • Hydrogen deuteride
  • Hydrogen diselenide
  • Hydrogen disulfide
  • Hydrogen ditelluride
  • Hydrogen fluoride
  • Hydrogen halide
  • Hydrogen iodide
  • Hydrogen isocyanide
  • Hydrogen peroxide
  • Hydrogen selenide
  • Hydrogen sulfide
  • Hydrogen telluride
  • Hydrogen thio-peroxide
  • Hydrogen-bridged cations
  • Hydroperoxyl
  • Hydrous oxide
  • Hypobromous acid
  • Hypochlorous acid
  • Hypofluorous acid
  • Hypoiodous acid
  • Hyponitrous acid
  • Hypophosphorous acid
  • Inorganic imide
  • Iodic acid
  • Isocyanic acid
  • Lead hydrogen arsenate
  • Lithium imide
  • Molybdic acid
  • Nitric acid
  • Nitrosylsulfuric acid
  • Nitroxyl
  • Perbromic acid
  • Perchloric acid
  • Periodic acid
  • Permanganic acid
  • Peroxydisulfuric acid
  • Peroxymonosulfuric acid
  • Phosphoric acid
  • Phosphorous acid
  • Pnictogen hydride
  • Polonium hydride
  • Polyhydride
  • Polysulfane
  • Properties of water
  • Pyrophosphoric acid
  • Selenous acid
  • Sodium bifluoride
  • Sulfamic acid
  • Sulfuric acid
  • Sulfurous acid
  • Telluric acid
  • Tellurous acid
  • Thiocarbonic acid
  • Thiosulfuric acid
  • Triatomic hydrogen
  • Trioxidane
  • Trisulfane
  • Water


5 Interesting Facts and Explanations

  1. Not only hydrogen is the lightest of all elements in the periodic table, but it’s also characterized by the lowest density among the other gaseous elements. 
  2. The hydrogen cycle refers to the natural cycle of hydrogen production and its consumption by living organisms. 
  3. There are twenty-two hydrogen atoms in the sugar molecule. Namely, the molecular formula of glucose is  C6H12O6, while the monosaccharides are typically described with the formula CnH2nOn.
  4. Hydrogen is the only chemical element whose isotopes have individual names. For instance, the 2H (or hydrogen-2) is named as deuterium (normal hydrogen – D), the 3H (or hydrogen-3) isotope’s name is tritium (T), etc. 
  5. Due to the fact that hydrogen has only one electron, it doesn’t have a second ionization after its first electron is removed in the process. In addition, hydrogen is the only chemical element that can exist without neutrons. 


Chemical Property and physical property of element Hydrogen

Symbol of Hydrogen: H
Name: Hydrogen
Atomic Number of Hydrogen: 1
Atomic Mass of Hydrogen: 1.00794
Uses of Hydrogen: Most hydrogen is used in the production of ammonia. Also used in balloons and in metal refining. Also used as fuel in rockets. Its two heavier isotopes are: deuterium (D) and tritium (T) used respectively for nuclear fission and fusion.
Description of Hydrogen: Light, odorless, colorless, tasteless inert gas. Second most abundant element in the universe. Sixth most abundant in the earth’s atmosphere.
Melting Point of Hydrogen: 13.96
Boiling Point of Hydrogen: 20.39
Group of Hydrogen: Non-Metal
Shells of Hydrogen: 1
Orbitals of Hydrogen: 1s1
Valence of Hydrogen: 1
Crystal Structure of Hydrogen: Hexagonal
Electro Negativity of Hydrogen: 2.2
Covalent Radius of Hydrogen: 0.32 Å
Ionic Radius of Hydrogen: 1.54 (+1) Å
Atomic Radius of Hydrogen: 0.79 Å
Atomic Volume of Hydrogen: 14.4 cm³/mol
Name Origin of Hydrogen: Greek: hydro (water) and genes (generate)
Discovered of Hydrogen By: Henry Cavendish
Year: 1766
Location: England
Pronounced of Hydrogen: HI-dreh-jen
Oxydation States of Hydrogen: ±1
Density of Hydrogen: 0.00008988 g/cm³

Hydrogen Facts

Read key information and facts about the chemical element Hydrogen

Atomic Number1
Atomic SymbolH
Atomic Weight1.00794
PhaseGas (Diatomic Gas )
Appearancecolorless gas
ClassificationOther Nonmetal
Group in Periodic Table1
Group Namelithium family
Period in Periodic Tableperiod 1
Block in Periodic Tables -block
Electronic Configuration1s1
Electronic Shell Structure (Electrons per shell)1
Melting Point14.01 K
Boiling Point20.28 K
CAS NumberCAS1333-74-0