Group 18 of the periodic table, once called the inert gases
Helium, neon, argon, krypton, xenon, radon and the synthetic oganesson
Science · Chemistry
Noble gases
1894–1900
Chemistry — Group 18
The noble gases are Group 18 of the periodic table — helium, neon, argon, krypton, xenon and the radioactive radon, with the synthetic oganesson at the foot. They were the last whole family of elements to be found, because they scarcely react with anything: Lord Rayleigh noticed that nitrogen obtained from air weighed slightly more than nitrogen made chemically, and with William Ramsay traced the difference in 1894 to argon, "the lazy one". Ramsay then found neon, krypton and xenon in 1898, and both men took Nobel Prizes in 1904. Their reputation for total inertness lasted until 1962, when Neil Bartlett made the first xenon compound.
How to spot them
- ▸Group 18, formerly called the inert or rare gases
- ▸The last whole family of elements to be discovered, and an entire new column of the periodic table
- ▸Their Greek names mean lazy, new, hidden and stranger
- ▸Full outer electron shells; almost no chemistry until 1962
- ▸Argon makes up nearly one per cent of the atmosphere, the third most abundant component
Key facts
Rayleigh noticed that nitrogen from air weighed more than nitrogen made chemically (1892)
The discrepancy of about half a per cent led him and Ramsay to argon in 1894
The names of three of them are Greek for 'new', 'hidden' and 'stranger'
Neon, krypton and xenon, all found by Ramsay and Travers in 1898
Neil Bartlett's 1962 xenon compound destroyed their reputation for inertness (1962)
Xenon hexafluoroplatinate, made after he saw that xenon and oxygen have similar ionisation energies
A complete outer shell of eight electrons — helium excepted — explains their reluctance to react
The octet rule is built around wanting to look like them
William Ramsay took the 1904 Nobel Prize in Chemistry for discovering a whole family of elements (1904)
Lord Rayleigh took that year's Physics prize, partly for argon
Georges Claude turned one of them into advertising signs from 1910
Neon's red-orange glow in a discharge tube; other colours use different gases or phosphors
Key ideas
- A filled valence shell leaves no low-energy orbital to share, so these atoms neither gain nor lose electrons easily; going down the group the outer electrons are less tightly held, which is why xenon and radon do have a chemistry and helium and neon essentially do not
- They exist as single atoms rather than molecules, giving them the lowest boiling points in each period
Quick-fire facts
- •Group 18: helium, neon, argon, krypton, xenon, radon and oganesson (element 118, named in 2016 after Yuri Oganessian)
- •Argon was found in 1894 by Lord Rayleigh and William Ramsay; its name is Greek for 'lazy' or 'inactive'
- •Ramsay and Morris Travers isolated neon, krypton and xenon from liquefied air in 1898; radon was identified by Friedrich Ernst Dorn around 1900 as 'radium emanation'
- •Ramsay received the 1904 Nobel Prize in Chemistry and Rayleigh the 1904 Nobel Prize in Physics
- •Argon makes up about 0.93 per cent of the atmosphere by volume, the third most abundant constituent after nitrogen and oxygen
- •Helium was named before it was isolated, having first been seen in the Sun's spectrum in 1868
- •Neil Bartlett made xenon hexafluoroplatinate in 1962, the first noble gas compound; xenon difluoride and xenon tetrafluoride followed within weeks
- •Radon is radioactive and, after smoking, the leading cause of lung cancer in many countries; it seeps out of granite bedrock
- •Uses: helium for cryogenics and lifting gas, neon for signs and lasers, argon as a welding and light-bulb fill gas, krypton and xenon in lamps, xenon as an anaesthetic and ion-thruster propellant
- •They were once called the rare gases, though argon is anything but rare, and the inert gases, a name abandoned after 1962
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Sources
- Los Alamos National Laboratory — Argon — Periodic Table of Elements
- The Nobel Foundation — The Nobel Prize in Chemistry 1904: William Ramsay