Helium
Fast facts
- Atomic number
- 02
- Symbol
- He
Helium is a chemical element. It has the chemical symbol He, atomic number 2, and atomic weight of about 4.002602. There are 9 isotopes of helium, only two of which are stable. These are 3 He and 4 He. 4 He is by far the most common isotope.
Helium is called a noble gas, because it does not regularly mix with other chemicals and form new compounds. It has the lowest boiling point of all the elements. It is the second most common element in the universe, after hydrogen, and has no color or smell. However, helium has a red-orange glow when placed in an electric field. Helium does not usually react with anything else. Astronomers detected the presence of helium in 1868, when its spectrum was identified in light from the Sun. This was before its discovery on Earth.
Helium is used to fill balloons and airships because its density is lighter than air. It does not burn, so is safe for that kind of use. It is also used in some kinds of light bulbs. People can breathe in helium: It makes their voices sound higher than it normally does. This may seem silly, but it can actually be quite dangerous as if they breathe in too much, hypoxia can injure or kill them as they are not breathing normal air. Breathing too much helium can also cause long-term effects to vocal cords.
Helium is created through the process of nuclear fusion in the Sun, and in similar stars. During this process, four hydrogen atoms are fused together to form one helium atom. On Earth it is made by the natural radioactive decay of heavy radioactive elements like thorium and uranium, although there are other examples. The alpha particles emitted by such decays consist of helium-4 nuclei.
Helium is a non-renewable resource. The Sun is hard to reach, and there is only a limited amount of it underground.
History
Helium was discovered by the French astronomer Pierre Janssen on August 18, 1868, as a bright yellow line in the spectrum of the chromosphere of the Sun. The line was thought to be sodium. On the same year, English astronomer, Norman Lockyer, also observed it and found that it was caused by a new element. Lockyer and English chemist Edward Frankland named the element helium, from the Greek word for the Sun, ἥλιος (helios).
Characteristics
Helium is the second least reactive noble gas after neon. It is the second least reactive of all elements. It is chemically inert and monatomic in all standard conditions. Helium is the least water-soluble monatomic gas.
Uses
Helium is used as a shielding gas in growing silicon and germanium crystals, in making titanium and zirconium, and in gas chromatography, because it is inert. Helium is used as a shielding gas in arc welding.
Helium is mixed with oxygen and other gases for deep underwater diving because it does not cause nitrogen narcosis.
Helium is also used to condense hydrogen and oxygen to make rocket fuel. It is used to remove the fuel and oxidizer from ground support equipment before the rocket launches. It is used to cool liquid hydrogen in space vehicles before the rocket launches.
Helium is used as a heat-transfer medium in some nuclear reactors that are cooled down by gas. Helium is also used in some hard disk drives. Helium at low temperatures is used in cryogenics.
Supply
Helium has become rare on Earth. If it gets free into the air it leaves the planet. Unlike hydrogen, which reacts with oxygen to form water, helium is not reactive. It stays as a gas. For many years after the 1925 Helium Act, the USA collected helium in a National Helium Reserve. American helium comes from wells in the Great Plains area. At present, more helium is supplied by Qatar than by the USA.
Several research organisations have released statements on the scarcity and conservation of helium. These organisations released policy recommendations as early as 1995 and as late as 2016 urging the United States government to store and conserve helium because of the natural limits to the helium supply and the unique nature of the element. For researchers, helium is irreplaceable because it is essential for producing very low temperatures. Helium at low temperatures is used in cryogenics, and in certain cryogenics applications. Liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging.
Written for younger readers
Helium, in simpler words
This version comes from Wikijunior, a set of books written for children aged 8 to 11. It is shorter and uses plainer language than the article above.
From Wikijunior: The Elements
NOTOC
Helium is seen on earth as a colorless and odorless gas. It is the clearest element, and even in a liquid state (which can only be achieved by either applying great pressure or extreme cold) it is almost completely transparent. However, in a plasma state (see below,) it emits a pinkish glow.
Helium was discovered in the Sun in 1868 by an astronomer, Sir Norman Lockyer. He was using a technique (then new) called spectrography, which breaks light into its separate colors. Each element produces a different spectral pattern of bright lines. Lockyer noticed a line in sunlight that didn’t match any known element and realized it belonged to a new element not found on Earth.
About 27 years later, in 1895, Sir William Ramsay discovered helium on Earth in a uranium mineral, cleveite. It was discovered independently about the same time by P.T. Cleve and Nils Langlet.
Helium gets its name from Helios, the Greek god of the sun.
Did You Know?
- Helium is the second most common element in the universe.
- Helium is a noble gas, so it doesn’t react very easily.
- Helium was used to learn that the structure of the atom had a dense nucleus and an electron cloud.
- Even at absolute zero, helium is still a liquid. It can only be solidified by applying extreme pressure to liquid helium.
- Near absolute zero, liquid helium will crawl along any surface; this is called superfluidity. Superfluid helium has zero viscosity (thickness.)
Helium is found very commonly in the universe, but not very common on Earth. Today, most helium comes from Texas and Kansas in the United States. It is extracted along with natural gas from wells drilled into the ground.
Helium is used to inflate balloons and blimps because it is the second lightest element (after Hydrogen), but doesn’t burn like Hydrogen can.
Helium is often used (along with oxygen and sometimes nitrogen) in breathing gas for divers that go very deep, where high pressure is needed. (Normal air at this pressure causes nitrogen narcosis, a state similar to being drunk.)
Liquid helium is the coldest liquid known (even at absolute zero, it remains a liquid) and is often used in cryogenic applications such as Magnetic Resonance Imaging (MRI), where the extreme cold makes it possible to create extreme magnetic fields.
Though helium is nontoxic, if you breathe in too much helium you can suffocate through lack of oxygen.
Where this page comes from
The article above is adapted from “Helium” on Simple English Wikipedia, by its contributors. We removed reference markers, navigation boxes and tables, expanded measurement templates into readable numbers, and kept the prose otherwise intact. The simpler version is adapted from Wikijunior on Wikibooks.
Both sources are published under CC BY-SA 4.0, so this page is published under the same licence. You may share and adapt it, including commercially, as long as you credit the original and keep the same licence.
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