Element of the week: Krypton

What do Superman, flash bulbs and lasers have in common?

by GrrlScientist for The Guardian | @GrrlScientist

Spectral colour lines created by Krypton. (Credit: McZusatz / public domain.)

This week’s element is Krypton, which has the symbol Kr and the atomic number 36. Krypton is another one of those noble gases, which I often think of as being indifferent gases because as a group, they are unreactive with mostly anything under any but the most extreme of circumstances.

Map of planet Krypton from Krypton Chronicles (Superman comics).

Besides being the name of the fictional home planet of the (also fictional) super-heroes Superman, Supergirl and Krypto the Superdog, Krypton has a few non-fictional uses here on Earth. For example, Krypton-based flash bulbs are used as a source of brilliant white light for high speed photography. Krypton also is mixed with Argon (another noble gas) inside energy-saving fluorescent lamps to reduce their power consumption. A mixture of Krypton and Xenon (yet another noble gas) are used to fill incandescent lamps, allowing higher operating temperatures. Together, these gases create a brighter light results that emits more of the blue portion of the light spectrum than conventional lamps.

Krypton has six stable and naturally-occurring isotopes. Krypton-81, a naturally-occurring radioactive product of atmospheric reactions, has a half-life of 230,000 years. Krypton-81 has been used for dating old (50,000–800,000 years) groundwater. Krypton-83 is used in magnetic resonance imaging (MRI) for imaging airways. Krypton-85 is one of the products of uranium fission and it has a half-life of 10.76 years. The light emitted by the Krypton-86 isotope (wavelength: 605.78 nanometers) was used to define the length of a metre, a standard that was internationally accepted in 1960. Krypton’s reign didn’t last long, however, and this definition was replaced in late 1983 by a new standard for the metre: the International Bureau of Weights and Measures (Bureau International des Poids et Mesures) defined the meter as the distance that light travels in a vacuum during 1/299,792,458 s.

As our favourite chemistry professor mentions in the embedded video, Krypton is used in the Krypton-Fluoride laser. Besides being a convenient instrument for burning holes in walls, this laser is used for experiments by the nuclear fusion energy research community:

Meet next week’s element: Rubidium!

You’ve already met these elements:

Bromine: Br, atomic number 35
Selenium: Se, atomic number 34
Arsenic: As, atomic number 33
Germanium: Ge, atomic number 32
Gallium: Ga, atomic number 31
Zinc: Zn, atomic number 30
Copper: Cu, atomic number 29
Nickel: Ni, atomic number 28
Cobalt: Co, atomic number 27
Iron: Fe, atomic number 26
Manganese: Mn, atomic number 25
Chromium: Cr, atomic number 24
Vanadium: V, atomic number 23
Titanium: Ti, atomic number 22
Scandium: Sc, atomic number 21
Calcium: Ca, atomic number 20
Potassium: K, atomic number 19
Argon: Ar, atomic number 18
Chlorine: Cl, atomic number 17
Sulfur: S, atomic number 16
Phosphorus: P, atomic number 15
Silicon: Al, atomic number 14
Aluminium: Al, atomic number 13
Magnesium: Mg, atomic number 12
Sodium: Na, atomic number 11
Neon: Ne, atomic number 10
Fluorine: F, atomic number 9
Oxygen: O, atomic number 8
Nitrogen: N, atomic number 7
Carbon: C, atomic number 6
Boron: B, atomic number 5
Beryllium: Be atomic number 4
Lithium: Li atomic number 3
Helium: He atomic number 2
Hydrogen: H atomic number 1

Video journalist Brady Haran is the man with the camera and the University of Nottingham is the place with the chemists. You can follow Brady on twitter @periodicvideos and the University of Nottingham on twitter @UniNottingham

Originally published at The Guardian on 4 November 2011.