Element 36 in our International Year of the Periodic Table series is krypton. Used in high-speed flash photography, krypton also has a link to the definition of the metre and can help detect covert nuclear facilities.

One of krypton’s common everyday uses is in some types of photographic flashes, particularly those for high-speed photography. It’s also used in some so-called neon lights, and some types of light bulbs also use krypton as a filler gas.

Krypton also has an unexpected link to the definition of the metre. Since 1983, the metre has been defined as the distance travelled by light in a vacuum in 1/299,792,458th of a second. However, between 1960 and 1983, it was defined as 1,650,763.73 wavelengths of light from a specified emission from the krypton-86 isotope.

Another isotope of krypton, krypton-85, is made during nuclear fuel reprocessing and released to the atmosphere. Consequently, its detection through atmospheric monitoring can aid the search for covert nuclear weapons facilities.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.