Periodic Table > Hydrogen
 

Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses and properties facts below.

 

Fact box terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (kgm-3)
Density is the weight of a substance that would fill 1 m3 (at 298 K unless otherwise stated).


Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).


CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact box

 
Group Melting point -259.1 oC, -434.38 oF, 14.05 K 
Period Boiling point -252.879 oC, -423.182 oF, 20.271 K 
Block Density (kg m-3) 89 (6 K) 
Atomic number Relative atomic mass 1.008  
State at room temperature Gas  Key isotopes 1H, 2
Electron configuration 1s1  CAS number 133-74-0 
ChemSpider ID 4515072 ChemSpider is a free chemical structure database
 

Uses and properties terminology


Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses and properties

 
Image explanation
Image based on the now familiar iconic atomic model proposed by Niels Bohr in 1913.
Appearance

A colourless, odourless gas. Its density is the lowest of all gases.

Uses

The low density of hydrogen made it a natural for one of its first practical uses - filling balloons. However it reacts vigorously with oxygen (to form water) and its future in filling airships stopped with the Hindenburg disaster, which caught fire. It is currently manufactured from methane gas, but is also produced by the electrolysis of water and aqueous salts. The gas is used to make such key materials as ammonia for agricultural fertiliser (the Haber Process) and cyclohexane and methanol, which are intermediates in the production of plastics and pharmaceuticals. Large quantities are used in the hydrogenation of oils to form fats. It has several other uses, including welding and the reduction of metallic ores, and liquid hydrogen is important in cryogenics and superconductivity studies as its melting point is just above absolute zero. Some see hydrogen gas as the clean fuel of the future - generated from water and returning to water when it is oxidised. Hydrogen-powered fuel cells are increasingly being seen as pollution-free sources of energy.

Biological role

Hydrogen is an essential element for life, only because it is present in almost all the molecules in living things, the building blocks of life, and, of course, in water. But it does not play a particularly active role remaining bonded to carbon and oxygen atoms whilst life’s chemistry takes place at the more active sites involving, for example, oxygen, nitrogen and phosphorus.

Natural abundance

Hydrogen is found in the sun and most of the stars, and is easily the most abundant element in the universe. The planet Jupiter is composed mostly of hydrogen, and there is a theory that in the interior of the planet the pressure is so great that metallic hydrogen is formed from solid molecular hydrogen. On Earth, hydrogen is found in the greatest quantities in water, but is present in the atmosphere only in tiny amounts - less than 1 part per million by volume. Due to its low molecular mass any hydrogen that does enter the atmosphere quickly escapes the Earth’s gravity.

 
Atomic data terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic data

 
Atomic radius, non-bonded (Å) 1.100 Covalent radius (Å) 0.32
Electron affinity (kJ mol-1) 72.743 Electronegativity
(Pauling scale)
2.200
Ionisation energies
(kJ mol-1)
 
1st
1312.049
2nd
-
3rd
-
4th
-
5th
-
6th
-
7th
-
8th
-
 
Bond enthalpies terminology

Covalent Bonds
The strengths of several common covalent bonds.

Bond enthalpies

 
Covalent bonds
H–F  568  kJ mol -1 H–I  298.3  kJ mol -1 H–H  435.9  kJ mol -1
H–Si  318  kJ mol -1 H–Ge  285  kJ mol -1 H–N  391  kJ mol -1
H–As  297  kJ mol -1 H–O  464  kJ mol -1 H–Si  364  kJ mol -1
H–Se  313  kJ mol -1 Br–H  366.3  kJ mol -1 Cl–H  432  kJ mol -1
H–P  321  kJ mol -1 C–H  413  kJ mol -1 C–H  435  kJ mol -1
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply risk

 
Scarcity factor Unknown
Country with largest reserve base Unknown
Crustal abundance (ppm) Unknown
Leading producer Unknown
Reserve base distribution (%) Unknown
Production concentration (%) Unknown
Total governance factor(production) Unknown
Top 3 countries (mined)
  • Unknown
Top 3 countries (production)
  • Unknown
 

Oxidation states and isotopes


Key for Isotopes


Half Life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Terminology


Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation states and isotopes

 
Common oxidation states 1, -1
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  1H 1.008 99.988
  2H 2.014 0.012
  3H 3.016 - 12.31 y  β- 
 

Pressure and temperature - advanced terminology


Molar Heat Capacity (J mol-1 K-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, it provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.


Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure and temperature data – advanced

 
Molar heat capacity
(J mol-1 K-1)
28.836 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - - - - - -
  Help text not available for this section currently

History

In the early 1500s the alchemist Paracelsus noted that the bubbles given off when iron filings were added to sulfuric acid were flammable. In 1671 Robert Boyle made the same observation. Neither followed up their discovery of hydrogen, and so Henry Cavendish gets the credit. In 1766 he collected the bubbles and showed that they were different from other gases. He later showed that when hydrogen burns it forms water, thereby ending the belief that water was an element. The gas was given its name hydro-gen, meaning water-former, by Antoine Lavoisier.


In 1931, Harold Urey and his colleagues at Columbia University in the US detected a second, rarer, form of hydrogen. This has twice the mass of normal hydrogen, and they named it deuterium.

  Help text not available for this section currently

Podcasts

Listen to Hydrogen Podcast
Transcript :

Chemistry in Its Element - Hydrogen


  (Promo)

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry

(End promo)

Meera Senthilingam

This week we hear what its like to be at the top, and number one, as we meet the King of the Elements.   Here's Brian Clegg.

Brian Clegg

Forget 10 Downing Street or 1600 Pennsylvania Avenue, the most prestigious address in the universe is number one in the periodic table, hydrogen. In science, simplicity and beauty are often equated - and that makes hydrogen as beautiful as they come, a single proton and a lone electron making the most compact element in existence.

Hydrogen has been around since atoms first formed in the residue of the Big Bang, and is the most abundant element by far. Despite billions of years of countless stars fusing hydrogen into helium it still makes up 75 per cent of the detectable content of the universe.

This light, colourless, highly flammable gas carries on its uniqueness by having the only named isotopes (and some of the best known at that), deuterium with an added neutron in the nucleus and tritium with two neutrons.

Hydrogen is an essential for life, the universe and just about everything. Life, in fact, is multiply dependent on it. Without hydrogen we wouldn't have the Sun to give us heat and light. There would be no useful organic compounds to form the building blocks of life. And that most essential substance for life's existence, water, would not exist.

It's only thanks to a special trick of hydrogen's that we can use water at all. Hydrogen forms weak bonds between molecules, latching onto adjacent oxygen, nitrogen or fluorine atoms. It's these hydrogen bonds that give water many of its properties. If they didn't exist, the boiling point of water would be below -70 degrees Celsius. Liquid water would not feature on the Earth.

Hydrogen was the unwitting discovery of Paracelsus, the sixteenth century Swiss alchemist also known as Theophrastus Philippus Aureolus Bombastus von Hohenheim. He found that something flammable bubbled off metals that were dropped into strong acids, unaware of the chemical reaction that was forming metal salts and releasing hydrogen, something a number of others including Robert Boyle would independently discover over the years. 

However, the first person to realize hydrogen was a unique substance, one he called 'inflammable air,' was Henry Cavendish, the noble ancestor of William Cavendish who later gave his name to what would become the world's most famous physics laboratory in Cambridge. Between the 1760s and 1780s, Henry not only isolated hydrogen, but found that when it burned it combined with oxygen (or 'dephlogisticated air' as it was called) to produce water. These clumsy terms were swept aside by French chemist Antoine Lavoisier who changed chemical naming for good, calling inflammable air 'hydrogen', the gene, or creator, of hydro, water.  

Because hydrogen is so light, the pure element isn't commonly found on the Earth. It would just float away. The prime components of air, nitrogen and oxygen, are fourteen and sixteen times heavier, giving hydrogen dramatic buoyancy. This lightness of hydrogen made it a natural for one of its first practical uses - filling balloons. No balloon soars as well as a hydrogen balloon. 

The first such aerial vessel was the creation of French scientist Jacques Charles in 1783, who was inspired by the Montgolfier brothers' hot air success a couple of months before to use hydrogen in a balloon of silk impregnated with rubber. Hydrogen seemed to have a guaranteed future in flying machines, reinforced by the invention of airships built on a rigid frame, called dirigibles in the UK but better known by their German nickname of Zeppelins, after their enthusiastic promoter Graf Ferdinand von Zeppelin.

These airships were soon the liners of the sky, carrying passengers safely and smoothly across the Atlantic. But despite the ultimate lightness of hydrogen it has another property that killed off airships - hydrogen is highly flammable. The destruction of the vast zeppelin the Hindenburg, probably by fire caused by static electricity, was seen on film by shocked audiences around the world. The hydrogen airship was doomed.

Yet hydrogen has remained a player in the field of transport because of the raw efficiency of its combustion. Many of NASA's rockets, including the second and third stages of the Apollo Program's Saturn V and the Space Shuttle main engines, are powered by burning liquid hydrogen with pure oxygen.

More recently still, hydrogen has been proposed as a replacement for fossil fuels in cars. Here it has the big advantage over petrol of burning to provide only water. No greenhouse gasses are emitted. The most likely way to employ hydrogen is not to burn it explosively, but to use it in a fuel cell, where an electrochemical reaction is used to produce electricity to power the vehicle.

Not everyone is convinced that hydrogen fuelled cars are the future, though. We would need a network of hydrogen fuel stations, and it remains a dangerous, explosive substance. At the same time, it is less efficient than petrol, because a litre of petrol has about three times more useful energy in it than a litre of liquid hydrogen (if you use compressed hydrogen gas that can go up to ten times more). The other problem is obtaining the hydrogen. It either comes from hydrocarbons, potentially leaving a residue of greenhouse gasses, or from electrolysing water, using electricity that may not be cleanly generated. 

But even if we don't get hydrogen fuelled cars, hydrogen still has a future in a more dramatic energy source - nuclear fusion, the power source of the sun. Fusion power stations are tens of years away from being practical, but hold out the hope of clean, plentiful energy.

However we use hydrogen, though, we can't take away its prime position. It is numero uno, the ultimate, the king of the elements.

Meera Senthilingam

So it's the most abundant element, is essential for life on earth, fuels space rockets and could resolve our fossil fuel dependents.   You can see why Brian Clegg classes Hydrogen as number one.   Now next week we meet the time keeper of the periodic table. 

Tom Bond 

One current use is in atomic clocks, though rubidium is considered less accurate than caesium. The rubidium version of the atomic clock employs the transition between two hyperfine energy states of the rubidium-87 isotope. These clocks use microwave radiation which is tuned until it matches the hyperfine transition, at which point the interval between wave crests of the radiation can be used to calibrate time itself. 

Meera Senthilingam

And to find out more of the roles of Rubidium join Tom Bond on next week's Chemistry in its Element.   Until then I'm Meera Senthilingam, thanks for listening and goodbye. 

(Promo)

Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements. 

(End promo)

  Help text not available for this section currently
  Help Text

Resources

Description :
A fast reaction with a burst of flame!
Description :
This is a safe and reliable way of demonstrating the photosensitive, free radical reaction between hydrogen and chlorine, which can be difficult to do safely in the lab.
Description :
A series of short, fun videos exploring the chemistry of the alkali metals, taken from a lecture by Dr. Peter Wothers at the University of Cambridge.
Description :
A series of short, fun videos exploring the chemistry of the alkali metals, taken from a lecture by Dr. Peter Wothers at the University of Cambridge.
Description :
A series of short screencasts to introduce the Chemistry of selected Elements These come from this website: http://www.chemistryvignettes.net/
Description :
In the beaker are test-tubes containing different gases - carbon dioxide, dinitrogen oxide, oxygen, chlorine and hydrogen. You may remove a test-tube only once and when you do so you must identify th...
 

Terms & Conditions


Images © Murray Robertson 1999-2011
Text © The Royal Society of Chemistry 1999-2011

Welcome to "A Visual Interpretation of The Table of Elements", the most striking version of the periodic table on the web. This Site has been carefully prepared for your visit, and we ask you to honour and agree to the following terms and conditions when using this Site.


Copyright of and ownership in the Images reside with Murray Robertson. The RSC has been granted the sole and exclusive right and licence to produce, publish and further license the Images.


The RSC maintains this Site for your information, education, communication, and personal entertainment. You may browse, download or print out one copy of the material displayed on the Site for your personal, non-commercial, non-public use, but you must retain all copyright and other proprietary notices contained on the materials. You may not further copy, alter, distribute or otherwise use any of the materials from this Site without the advance, written consent of the RSC. The images may not be posted on any website, shared in any disc library, image storage mechanism, network system or similar arrangement. Pornographic, defamatory, libellous, scandalous, fraudulent, immoral, infringing or otherwise unlawful use of the Images is, of course, prohibited.


If you wish to use the Images in a manner not permitted by these terms and conditions please contact the Publishing Services Department by email. If you are in any doubt, please ask.


Commercial use of the Images will be charged at a rate based on the particular use, prices on application. In such cases we would ask you to sign a Visual Elements licence agreement, tailored to the specific use you propose.


The RSC makes no representations whatsoever about the suitability of the information contained in the documents and related graphics published on this Site for any purpose. All such documents and related graphics are provided "as is" without any representation or endorsement made and warranty of any kind, whether expressed or implied, including but not limited to the implied warranties of fitness for a particular purpose, non-infringement, compatibility, security and accuracy.


In no event shall the RSC be liable for any damages including, without limitation, indirect or consequential damages, or any damages whatsoever arising from use or loss of use, data or profits, whether in action of contract, negligence or other tortious action, arising out of or in connection with the use of the material available from this Site. Nor shall the RSC be in any event liable for any damage to your computer equipment or software which may occur on account of your access to or use of the Site, or your downloading of materials, data, text, software, or images from the Site, whether caused by a virus, bug or otherwise.


We hope that you enjoy your visit to this Site. We welcome your feedback.

References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.