Periodic Table > Helium
 

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 18  Melting point -272.2 oC, -457.96 oF, 0.950 K 
Period Boiling point -268.93 oC, -452.074 oF, 4.220 K 
Block Density (kg m-3) 120 (4.22 K) 
Atomic number Relative atomic mass 4.003  
State at room temperature Gas  Key isotopes 4He 
Electron configuration 1s2  CAS number 7440-59-7 
ChemSpider ID 22423 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 of the sun and solar flares reflecting the origin of the element’s name from the Greek “helios”, sun. Helium was detected in the sun by its spectral lines many years before it was found on Earth.

Appearance

A colourless, odourless gas that is totally unreactive.

Uses

Helium is widely used as an inert gas shield for arc welding; as a protective gas in growing silicon and germanium crystals, and in titanium and zirconium production. It is also used as a cooling medium for nuclear reactors, and as a gas for supersonic wind tunnels. A mixture of 80% helium and 20% oxygen is used as an artificial atmosphere for divers and others working under pressure. Helium is extensively used for filling balloons as it is a much safer gas than hydrogen. One of the recent largest uses for helium has been for pressurising liquid fuel rockets.

Biological role
Helium has no known biological function, but it is non-toxic.
Natural abundance

After hydrogen, helium is the second most abundant element in the universe. It is present in all stars. It was and still is being formed from alpha particle decay of radioactive elements in the earth. Some of the helium formed seeps up to the Earth’s atmosphere which contains about 5 parts per million by volume, but this is a dynamic balance, with the light helium atoms continually escaping to outer space. The major sources are from natural gas wells in Texas, Oklahoma and Kansas which can contain up to 7% helium.

 
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) 1.400 Covalent radius (Å) 0.37
Electron affinity (kJ mol-1) Not stable Electronegativity
(Pauling scale)
Unknown
Ionisation energies
(kJ mol-1)
 
1st
2372.323
2nd
5250.512
3rd
-
4th
-
5th
-
6th
-
7th
-
8th
-
 

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 6.5
Country with largest reserve base USA
Crustal abundance (ppm) Unknown
Leading producer USA
Reserve base distribution (%) 40.80
Production concentration (%) 80.30
Total governance factor(production) 8
Top 3 countries (mined)
  • 1) USA
  • 2) Qatar
  • 3) Algeria
Top 3 countries (production)
  • 1) USA
  • 2) Algeria
  • 3) Russia
 

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 Unknown
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  3He 3.016 0
  4He 4.003 100
 

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)
20.786 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)
- - - - - - - - - - -
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History

In 1868, Pierre J. C. Janssen travelled to India to measure the solar spectrum during a total eclipse and observed a new yellow line which indicated a new element. Joseph Norman Lockyer recorded the same line by observing the sun through London smog and, assuming the new element to be a metal, he named it helium.


In 1882, the Italian Luigi Palmieri found the same line the spectrum of gases emitted by Vesuvius, as did the American William Hillebrand in 1889 when he collected the gas given off by the mineral uraninite (UO2) as it dissolves in acid. However, it was Per Teodor Cleve and Nils Abraham Langer at Uppsala, Sweden, in 1895, who repeated that experiment and confirmed it was helium and measured its atomic weight.

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Podcasts

Listen to Helium Podcast
Transcript :

Chemistry in Its Element - Helium


  (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)

 

Chris Smith

 

Hello, this week we're almost at the top of the periodic table because we're taking a look at the lighter than air gas Helium.   But for this chemist a helium filled bobbing balloon is actually a source of pain and not a source of pleasure.   Here's Peter Wothers.

 

Peter Wothers

 

We are all familiar with the lighter-than-air gas helium, but whenever I see a balloon floating on a string, I feel a little sad.   It's not because I'm a miserable old so-and-so - it's just because, unlike the happy child on the other end of the string, I am aware of the valuable resource that's about to be lost forever.

 

Helium is the second most abundant element in the universe, but here on earth, it's rather rare.   Most people guess that we extract helium from the air, but actually we dig it out of the ground.   Helium can be found in certain parts of the world, notably in Texas, as a minor component in some sources of natural gas.   The interesting thing is how this gas gets into the ground in the first place.   Unlike virtually every other atom around us, each atom of helium has been individually formed after the formation of the earth.

 

The helium is formed during the natural radioactive decay of elements such as uranium and thorium.   These heavy elements were formed before the earth but they are not stable and very slowly, they decay. One mode of decay for uranium is to emit an alpha-particle.   This alpha-particle is actually just the heart of a helium atom - its nucleus. Once it has grabbed a couple of electrons, a helium atom has been born.

This decay process for uranium is incredibly slow; the time it takes a given quantity of uranium to halve, its so-called half-life, is comparable to the age of the earth.   This means that helium has been continuously generated ever since the earth was formed.   Some of the gas might eventually creep through the earth and escape into the atmosphere; fortunately, when conditions are right, some is trapped underground and can be harvested for our use.

 

The situation is very different in space.   The sun is comprised of about 75% by mass of hydrogen and 24% of helium.   The remaining one percent is made up of all the heavier elements.   In the high temperatures of the sun, the hydrogen nuclei are fused together to eventually form helium.   This fusion process, whereby heavier atoms are made from lighter ones, liberates vast amounts of energy.   Recreating the process on earth may be the answer to our energy problems in the future.

 

Since helium makes up about a quarter of the mass of the sun, it is not surprising that its presence was detected there over 100 years ago.   What is perhaps surprising, is that helium was discovered in space 26 years before it was found on earth.  

It has been known for hundreds of years that certain elements impart characteristic colours to a flame - a fact crucial to the coloured fireworks that we enjoy.   Copper, for example, gives a green colour, whereas sodium gives a yellow colour.   It is actually possible to identify elements by the careful examination of such coloured flames.    The light is split up into a spectrum using a prism or diffraction grating in an instrument called a spectroscope.   Rather than seeing a continuous rainbow of colours, a series of sharp coloured lines is formed.   This series of lines is characteristic of the particular element and acts as a sort of fingerprint.


In the 19th century, scientists turned their spectroscopes to the sun and began to detect certain metals there, including sodium, magnesium, calcium and iron.   In 1868 two astronomers, Janssen and Lockyer, independently noticed some very clear lines in the solar spectrum that did not match up to any known metals.   While other astronomers of the time were unsure, Lockyer suggested these unidentified lines belonged to a new metal which he named Helium after the Greek personification of the sun, Helios.   For over 20 years, no sign of the metal helium was detected on earth and Lockyer began to be mocked for his mythical element.   However, in 1895 the chemist William Ramsay detected helium in the gas given out when a radioactive mineral of uranium was treated with acid.   The helium formed from the radioactive decay had been trapped in the rock but liberated when the rock was dissolved away in the acid.

 

Finally Lockyer's element had been discovered on earth, but it was no metal, rather an extremely unreactive gas.   To this day, helium remains the only non-metal whose name ends with the suffix -ium, an ending otherwise exclusively reserved for metals.

 

Aside from being used to fill balloons, both for our entertainment, and for more serious purposes, such as for weather balloons, helium is used in other applications which depend on its unique properties.   Being so light, and yet totally chemically inert, helium can be mixed with oxygen in order to make breathing easier.   This mixture, known as heliox, can help save new-born babies with breathing problems, or help underwater divers safely reach the depths of the oceans.   At minus 269 degrees centigrade, liquid helium has the lowest boiling point of any substance.   Because of this, it is used to provide the low temperatures needed for superconducting magnets, such as those used in most MRI scanners in hospitals.

 

In many facilities where helium is used, it is captured and reused.   If it isn't, it escapes into the air.   But it doesn't simply accumulate in the atmosphere.   Helium is so light that it can escape the pull of the earth's gravitational field and leave our planet forever.   This is the fate of the helium in our balloons.   Whereas it may be possible to reclaim and recycle other elements that we have used and discarded, when we waste helium, it is lost for good.   In 100 years time, people will look back with disbelief that we wasted this precious, unique element by filling up party balloons.

 

Chris Smith

 

Cambridge University's Peter Wothers telling us the tale of element number two, Helium.   Next time we're off to 18th century Scotland and an element that was the wrong colour.

 

Richard Van Noorden

 

In 1787, an intriguing mineral came to Edinburgh from a Lead mine in a small village on the shores of Loch Sunart, Argyll. At that time, the stuff was thought to be some sort of Barium compound. Other chemists, such as Edinburgh's Thomas Hope later prepared a number of compounds with the element, noting that it caused the candle's flame to burn red, while Barium compounds gave a green colour. 

 

Chris Smith

 

And that's because it wasn't Barium at all, it was Strontium and Richard Van Noorden will be here to explain how, amongst other things, it's shown us that Roman gladiators weren't meat eaters they were in fact vegetarians.   That's next week's Chemistry in its Element and I hope you can join us.   I'm Chris Smith, thank you 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)

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Resources

Description :
The activity sets some critical thinking and pattern spotting tasks in the context of the noble gases. The students are given data that can be manipulated to show a directly proportional relationship,...
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A teaching resource on Group 8 (18) - The Noble Gases, supported by video clips from the Royal Institution Christmas Lectures® 2012.
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A series of short videos of fun demonstrations about the chemistry of the gases in our atmosphere, taken from a lecture by Dr. Peter Wothers of the University of Cambridge.
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A series of short experiments and demonstrations about the chemistry of light, taken from a lecture by Peter Wothers from the University of Cambridge
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This demonstration is based on an idea of Georgina Batting, head of science at Blundell's School. Igniting balloons filled with hydrogen gas is an exciting, well-known and much loved demonstration. B...
Learn Chemistry: Your single route to hundreds of free-to-access chemistry teaching resources.
 

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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.