What Is Helium?
QUICK ANSWER
Helium is a chemical element with atomic number 2 and the symbol He. It is the second lightest and second most abundant element in the universe, after hydrogen. As a noble gas, helium does not react with other elements, which is why it is used in balloons, MRI machines, and high-tech cooling applications.
Helium is the only element discovered in space before being found on Earth. It was identified in the sun's spectrum in 1868, 27 years before being isolated on Earth. Today helium fills party balloons and makes voices squeaky, but its most important uses are in scientific equipment, medical imaging, and aerospace where its unique properties cannot be substituted.
Where is helium on the periodic table?
Helium has atomic number 2, the symbol He, and sits in group 18, the noble gases. Each atom has two protons, two electrons, and usually two neutrons. Helium has the smallest atomic radius of any element after hydrogen and the highest first ionization energy, meaning its electrons are extremely difficult to remove. Two stable isotopes exist: He-4 (over 99.99%) and He-3 (extremely rare, used in research). Helium does not bond with any other element under normal conditions because its outer electron shell is already full and stable.
What are the properties of helium?
Helium is a colorless, odorless, tasteless, non-toxic gas at room temperature. It liquefies at -269°C, just 4 degrees above absolute zero, and never freezes at normal pressure (a unique property). Liquid helium has remarkable behaviors, including superfluidity, where it flows without any viscosity. Helium is about seven times less dense than air, which is why helium balloons rise. It is chemically inert, meaning it does not burn, react, or form compounds under normal conditions, making it extremely safe to handle, though displacing oxygen can cause suffocation.
What is helium used for?
Helium's main industrial uses depend on its extreme cold or its inertness. Liquid helium cools the superconducting magnets in MRI machines, NMR spectrometers, and particle accelerators. Helium gas pressurizes rocket fuel tanks, including those on modern rockets. The semiconductor industry uses helium during chip manufacturing. Welding uses helium to shield welds from atmospheric reactions. Party balloons use about 8% of global helium supply, an amount many scientists consider wasteful given helium's scarcity and irreplaceable scientific uses.
Why is helium running out?
Helium on Earth comes from radioactive decay of uranium and thorium deep underground, accumulating in natural gas deposits over millions of years. Once released to the atmosphere, helium is too light to be retained by Earth's gravity and drifts off into space, lost forever. Global helium reserves are concentrated in a few US, Qatar, and Russian fields, and consumption is outpacing discovery. Several helium shortages have occurred over the past two decades, driving prices up and threatening MRI scanner operations and scientific research globally.
Helium is the lightest noble gas and one of the universe's most abundant elements, but a surprisingly scarce resource on Earth. From MRI machines to rockets to party balloons, helium's unique properties make it irreplaceable for many uses, even as global supply remains limited.
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