Science · Chemistry

Helium

1868 (in the Sun); 1895 (on Earth)

Chemistry — noble gases

Helium is element 2, and the only element found beyond the Earth before it was found on it. During the total solar eclipse of 18 August 1868 Jules Janssen recorded an unexplained yellow line in the Sun's chromosphere; Norman Lockyer, seeing the same line from London, argued that it belonged to a new element and with Edward Frankland named it after Helios. Not until 1895 did William Ramsay — and independently Per Teodor Cleve and Nils Langlet in Uppsala — coax it out of the uranium ore cleveite. It has the lowest boiling point of any element and will not freeze at atmospheric pressure at any temperature.

How to spot them

▸Discovered in the Sun twenty-seven years before it was found on Earth
▸The lowest boiling point of any element, 4.22 K
▸Will not solidify at atmospheric pressure however cold it gets
▸Second most abundant element in the universe, yet scarce on Earth
▸Below about 2.17 K it becomes a superfluid and creeps up the walls of its container

Key facts

First detected as an unexplained yellow line in the Sun's chromosphere in 1868 (1868)

Jules Janssen at the eclipse in India; Norman Lockyer independently from London

Named after the Greek sun god by Lockyer and Edward Frankland

From helios — the only element named for the body in which it was first seen

The element with the lowest boiling point, 4.22 K

Liquefied by Heike Kamerlingh Onnes at Leiden in 1908, opening up low-temperature physics

The only element that will not freeze at atmospheric pressure at any temperature

Zero-point motion keeps it liquid; about 25 atmospheres are needed to solidify it

Below 2.17 K, the lambda point, it flows with zero viscosity

Superfluidity, found by Kapitsa and by Allen and Misener in 1937

Extracted commercially from natural gas, where alpha decay has trapped it underground

An alpha particle is a nucleus of this element; the United States and Qatar dominate supply

Isolated on Earth in 1895 by William Ramsay from the uranium ore cleveite (1895)

Per Teodor Cleve and Nils Langlet did the same independently at Uppsala

Key ideas

Its nucleus, two protons and two neutrons, is exceptionally tightly bound — which is why alpha decay spits out helium nuclei and why fusion in stars piles up at helium
Quantum zero-point energy exceeds the weak attraction between helium atoms, so no amount of cooling alone will freeze it

Quick-fire facts

•Atomic number 2, symbol He; the second lightest element and the second most abundant in the universe, about a quarter of ordinary matter by mass
•First seen as the D3 spectral line during the total eclipse of 18 August 1868; named by Norman Lockyer and Edward Frankland after Helios
•Isolated on Earth in 1895 by William Ramsay, and independently by Per Teodor Cleve and Nils Langlet, from the uranium mineral cleveite
•Boiling point 4.22 K (−268.93 °C), the lowest of any element; first liquefied by Heike Kamerlingh Onnes in 1908
•Helium-4 becomes a superfluid below 2.17 K, the lambda point; Pyotr Kapitsa shared the 1978 Nobel Prize in Physics for work on it
•Helium-3 is a rare isotope used in dilution refrigerators and neutron detectors
•Most terrestrial helium is radiogenic — alpha particles from uranium and thorium decay, trapped in natural gas fields
•It is light enough to escape Earth's gravity once released, so it is effectively non-renewable on human timescales
•Its largest modern use is cooling the superconducting magnets of MRI scanners and particle accelerators, not filling balloons
•Inhaling it raises the pitch of the voice because sound travels roughly three times faster in helium than in air, shifting the vocal tract's resonances

Drill it — 10 cards

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Sources

Science History Institute — The High-Flying, Death-Defying Discovery of Helium
Los Alamos National Laboratory — Helium — Periodic Table of Elements
Smithsonian Magazine — How Scientists Discovered Helium, the First Alien Element, 150 Years Ago