Helium Element Facts

The chemical element helium is classed as a noble gas and a nonmetal. It was discovered in 1895 by William Ramsay.

Data Zone

Classification:	Helium is a noble gas and a nonmetal
Color:	colorless
Atomic weight:	4.00260
State:	gas
Melting point:	-272.2 oC, 0.95 K
Note: At normal atmospheric pressure, helium does not solidify and so has no melting point. The melting point quoted above is under a pressure of 25 atmospheres.
Boiling point:	-268.9 oC, 4.2 K
Electrons:	2
Protons:	2
Neutrons in most abundant isotope:	2
Electron shells:	2
Electron configuration:	1s2
Density @ 20oC:	0.0001787 g/cm3

Show more, including: Heats, Energies, Oxidation,
Reactions, Compounds, Radii, Conductivities

Atomic volume:	27.2 cm3/mol
Structure:	usually hexagonal close-packed
	(v.high pressure needed to solidify helium)
Specific heat capacity	5.193 J g-1 K-1
Heat of fusion	0.0138 kJ mol-1
Heat of atomization	0
Heat of vaporization	0.0845 kJ mol-1
1st ionization energy	2372.3 kJ mol-1
2nd ionization energy	–
3rd ionization energy	–
Electron affinity	0 kJ mol-1
Minimum oxidation number	0
Min. common oxidation no.	0
Maximum oxidation number	0
Max. common oxidation no.	0
Electronegativity (Pauling Scale)	–
Polarizability volume	0.198 Å3
Reaction with air	none
Reaction with 15 M HNO3	none
Reaction with 6 M HCl	none
Reaction with 6 M NaOH	none
Oxide(s)	none
Hydride(s)	none
Chloride(s)	none
Atomic radius	31 pm
Ionic radius (1+ ion)	–
Ionic radius (2+ ion)	–
Ionic radius (3+ ion)	–
Ionic radius (1- ion)	–
Ionic radius (2- ion)	–
Ionic radius (3- ion)	–
Thermal conductivity	0.15 W m-1 K-1
Electrical conductivity	–
Freezing/Melting point:	-272.2 oC, 0.95 K

Nasa: Ionized helium atoms at about 60,000 °C in the Sun’s chromosphere emit the ultraviolet light seen in this image.

Helium was made in the first three minutes of the universe’s existence, when temperatures everywhere were high enough for nuclear fusion to occur. This short, high energy phase is represented at the very bottom of the diagram. Helium is also made by nuclear fusion of hydrogen in stars like our own. Image: Gnixon

Helium on earth comes from nuclear fission of radioactive elements such as uranium. Here a radioactive nucleus emits a helium nucleus (also known as an alpha particle). Image: Inductiveload

Helium’s spectrum with prominent yellow line. Image: Nasa

William Ramsay pointing to the periodic table’s final column containing the noble (or inert) gases. Ramsay was awarded the Nobel Prize for Chemistry in 1904 for his work in the discovery of the inert gases. Image: Vanity Fair

Discovery of Helium

The story of helium’s discovery is interwoven with the discovery of the nature of stars.

At one time people believed we would never know what stars are made of. In 1835 French philosopher Auguste Comte declared, “we shall never be able by any means to study their chemical composition.” ⁽¹⁾

Comte thought we could only learn what star-stuff was if we could get it into the laboratory.

Despite Comte’s pessimism, the method for the discovery of helium and the compositions of the stars had already been found. In 1814 German physicist Joseph Fraunhofer had taken Isaac Newton’s method of splitting sunlight using a prism and had made a crucial advance. Fraunhofer had noticed dark lines in the rainbow of colors coming from sunlight split by a prism; the lines he saw were the first ever observation of a star’s spectrum. ^{(2), (3)}

In 1859/60 German scientists Gustav Kirchhoff and Robert Bunsen made enormous leaps in the science of spectroscopy, including the discovery that the dark lines Fraunhofer had seen were like a substance’s fingerprint.

The scene was set for Kirchhoff and Bunsen to discover new elements by studying light from substances when they were burning.

In 1860 they discovered cesium by its blue spectral lines and in 1861 rubidium from two red spectral lines. Then William Crookes discovered thallium in 1861 after observing a bright green spectral line.

Kirchhoff and Bunsen looked at the sun’s spectrum and were able to conclude that iron was present in its glowing atmosphere. ⁽⁴⁾

For helium’s discovery, a few more years were needed. In August 1868 the first total eclipse since Kirchhoff and Bunsen’s work had been published was due.

French astronomer Pierre Janssen was waiting for an eclipse in order to observe prominences in the sun’s corona using a spectroscope. In the two weeks following the eclipse Janssen developed a method of recording prominences’ spectra without the need for an eclipse. In these spectra, he observed a yellow line. ⁽⁵⁾

The line was in a similar but not identical position to lines in sodium’s spectrum. These were called the D₁ and D₂ lines. English scientist Norman Lockyer studied the new yellow line; later it would be called the D₃ line. He published his study of the line, aware it might be caused by a new element:

“…so then we knew that we were not dealing with hydrogen; hence we had to do with an element which we could not get in our laboratories, and therefore I took upon myself the responsibility of coining the word helium, in the first instance for laboratory use.” ⁽⁶⁾

The name helium came from the Greek word for the sun, helios.

Lockyer and Edward Frankland, his coworker, had a number of other ideas about the possible causes of the yellow line and therefore did not announce a new element.

By 1871, other scientists were aware of the situation. Lord Kelvin discussed “reflection of the light of the glowing hydrogen and ‘helium’ round the sun.” The use of ‘helium’ is followed by a footnote to explain it:

“Frankland and Lockyer find the yellow prominences to give a very decided bright line not far from D, but hitherto not identified with any terrestrial flame. It seems to indicate a new substance, which they propose to call Helium.” ⁽⁷⁾

Helium’s existence was not, however, accepted by everyone. ⁽⁵⁾

All doubts were dispelled when Scottish chemist William Ramsay isolated helium in 1895 in London. Ramsay had codiscovered argon in 1894; argon was the first of the noble gases to be discovered. In 1895 he read a paper by William Hillebrand describing an unreactive gas that was released when acid was added to the uranium mineral, uranite. Hillebrand believed the gas was nitrogen. [We now know that uranium emits helium during radioactive decay. Radioactivity’s existence was not recognized until 1896 when Henri Becquerel’s work was published.]

Ramsay, who believed the gas might contain argon, repeated Hillebrand’s experiment using another uranium mineral, cleveite, and collected the gas.

His spectroscope indicated the presence of nitrogen, argon and one other gas. Ramsay suspected it could be helium, because there appeared to be a D₃ line. ⁽⁸⁾ Aware that Lockyer and William Crookes had a better spectroscope than his, he sent them a sample of the gas. Unfortunately the sample was not suitable, so Lockyer obtained a sample of uranite, extracted the gas and studied it by spectroscope. He writes: ⁽⁸⁾

“One by one the unknown lines I had observed in the sun in 1868 were found to belong to the gas.”

The gas’s spectrum was identical to the sun’s ‘helium.’ A new element won its place in the periodic table.

Visit Chemicool’s Cool Helium Facts Page.

Most people know what speaking after breathing helium sounds like. If you don’t, listen here. And what about sulfur hexafluoride?

At close to absolute zero, helium becomes a superfluid. How will it behave?

Appearance and Characteristics

Harmful effects:

Helium is not known to be toxic.

Characteristics:

Helium is a light, odorless, colorless, inert, monatomic gas. It can form diatomic molecules, but only weakly and at temperatures close to absolute zero.

Helium has the lowest melting point of any element and its boiling point is close to absolute zero.

Unlike any other element, helium does not solidify but remains a liquid down to absolute zero (0 K) under ordinary pressures.

The voice of someone who has inhaled helium temporarily sounds high-pitched.

Uses of Helium

Magnetic resonance imaging (MRI) is the biggest user of helium. The helium is used to cool MRI scanners’ superconducting magnets.

Helium is used for filling balloons (blimps) and for pressurizing liquid fuel rockets.

Mixtures of helium and oxygen are used as an artificial ‘air’ for divers and others working under pressure. Helium is used instead of the nitrogen in normal air because, after a long dive, helium leaves the body faster than nitrogen, allowing faster decompression.

Helium is used as a gas shield in the vicinity of arc welding preventing, for example, any reaction of hot metal welds with oxygen. The gas is used in the semi-conductor industry to provide an inert atmosphere for growing silicon and germanium crystals. It is also used as a high temperature gas in titanium and zirconium production, and as a carrier gas in gas chromatography.

Abundance and Isotopes

Abundance earth’s crust: 8 parts per billion by weight, 43 parts per billion by moles

Abundance solar system: 23 % by weight, 7.4 % by moles

Cost, pure: $5.2 per 100g

Cost, bulk: $ per 100g

Source: Nearly all the helium on Earth is the result of radioactive decay. The major sources of helium are from natural gas deposits in wells in Texas, Oklahoma and Kansas. Helium is extracted by fractional distillation of the natural gas, which contains up to 7% helium.

Isotopes: Helium has 8 isotopes whose half-lives are known, with mass numbers 3 to 10. Naturally occurring helium is a mixture of its two stable isotopes, ³He and ⁴He with natural abundances of 0.0001% and 99.999% respectively.

References

1. Auguste Comte, Cours de Philosophie Positive at Project Gutenberg
2. Keith J. Laidler, The World of Physical Chemistry, 1993, p179.
3. The Era of Classical Spectroscopy, from MIT Spectroscopy.
4. Gerard G. Emch, Mathematical and Conceptual Foundations of 20th-Century Physics., 1984, Elsevier Science Publishers, p211
5. Helge Kragh, The Solar Element: A Reconsideration of Helium’s Early History., 2009, Annals of Science, 66:2, p157-182.
6. J. Norman Lockyer, The Growth of our Knowledge of Helium., Science Progress, 1896, Vol 5., p249
7. W. Thomson, Presidential Address, British Association for the Advancement of Science, 1871, (Address. XCIX).
8. Sir Norman Lockyer, The Sun’s Place in Nature., 1897, p47-48

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