Light fantastic

Following on from radon and argon, two more elements in Group 18: neon and xenon, both of which find use in bright and showy lighting.

We are all familiar with the bright “neon” lights used in advertising displays and in signage such as exit arrows. Neon lends itself for this purpose as it emits a strong crimson light in a gas-discharge tube, a property that played a part in its discovery. It was this red glow that proved to Sir William Ramsey and Morris W Travers that they had identified a new element when they isolated it from air in 1898. After a suggestion to name it novum for “new” by Ramsey’s thirteen-year-old son, they translated from Latin to Greek and it became neon. Even though the other colours of neon lights are created using different gases and fluorescent coatings on the tubes, they have collectively become known by the name of the gas in the original red variety.

The applications of xenon to lighting are not quite so well known (appropriately, as its name means “stranger”) but nevertheless we are all familiar with them. In a standard gas-discharge tube xenon gives a lilac-blue glow, but with a higher current density a bright white flash is emitted. Xenon flash tubes have been used in photography since their invention in the 1930s by Harold Edgerton, a professor of electrical engineering at MIT, also known as “Papa Flash”. Xenon is also used in strobe lighting, lighthouse lamps, super-bright car headlights and fluorescence microscopy.

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