Here’s a ray of sunshine on a gloomy day (well at least here in Tooting). My second blog is the second element in the periodic table:
Atomic number: 2
Discovered: 1868 (Jules Janssen/Norman Lockyer)
This lighter-than-air gas is the second-most abundant element in the universe after hydrogen.
Helium is a drop of sunshine – it takes its name from helios, the Greek god and name for the Sun. It was the first of the shy and retiring noble gases to be found. Because of their extreme unreactivity and unwillingness to mix with any other members of the periodic table, the noble gases are very good at hiding out in our very midst! They are all around us, but like secret agents mingle unnoticed in the crowd, careful not to take part in everyday affairs.
In fact, helium was spotted in the Sun before it was found on Earth. The gas gave itself away as an unidentified yellow band in the Sun’s spectrum, first observed in 1868 by the French scientist, Pierre Jules César Janssen.
With just two protons and two neutrons in its nucleus, helium is extremely light and this makes problems for it sticking around on Earth. Unless stopped, its buoyancy lifts it high up and it is easily accelerated to speeds that will cause it to exit the atmosphere altogether. It was many years until it was tracked down – by William Ramsey and Maurice Travers (more about these guys in later posts) in 1895 – trapped inside the mineral cleveite (a type of uraninite).
Despite its scarcity on Earth, helium is the second most common element in the universe. It is created on Earth by radioactive decay but these piffling amounts aside, most helium harks back to the first wave of atom (nucleus) creation following the Big Bang. It’s also made in stars (see below).
Liquid helium is a supreme coolant because it remains liquid all the way to absolute zero. (It will only go solid if subjected to about 25 times atmospheric pressure.) It is used to keep superconducting magnets in medical MRI scanners at their sub-freezing operating temperatures.
Helium’s lightness makes it useful as a lifting gas. As well as brightly coloured party balloons, it also raises weather balloons and airships to the heavens. Heavier than hydrogen, it nevertheless has the distinct advantage that is not explosive.
Most helium available today is refined from natural gas.
Stars fusing hydrogen atoms in their central cores – at temperatures around 10 million ºC – also produce fresh helium.
It may be created hot but helium has the lowest boiling point around – at normal pressures it won’t freeze solid. Near absolute zero, it transforms into a superfluid called Helium II – this supervillain stuff can defy gravity and “creep” out of its container. Freaky!
Human body & nature
Minutes before deep diving, human divers breathe a mixture of nitrogen, oxygen and helium to stop them suffering from the “raptures of the deep” – a kind of floppy silliness – while underwater.
The Large Hadron Collider (LHC) uses nearly 96 tonnes of liquid helium to keep the superconducting magnets at a steady –217.25 ºC.
In 2008, breadcrumbs from a rogue baguette shorted out the LHC’s super-conducting magnets, breaking the 10-tonne magnets from their housing and letting 6 tonnes of liquid helium leak out.
Melting point: –272.2 °C (–457.96 °F)
Boiling point: –268.93 °C (–452.074 °F)
Density: 120 kg/m3
Relative atomic mass: 4.003
State at room temperature: gas
Biggest helium producers: USA, Algeria (2008), Russia
Links, resources & sources