Krypton
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| General Properties | |
|---|---|
| Atomic number | 36 |
| Atomic mass | 83.798amu |
| Atomic radius | 88pm |
| Electron Configuration | [Ar] 3d10 4s2 4p6 |
| Density | 0.00374 g/cm3 |
| Melting point | -157.37°C |
| Boiling point | -153.42°C |
| First discovered/ developed | 1898 |
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Description and uses
Krypton is the third noble gas, and is the 36th element in the periodic table. It occurs naturally in air, or it can be synthesised from nuclear fission of
Uranium. It was first discovered in 1898 by William Ramsay. He was evaporating liquid air when he found a residue that evaporated at a higher melting point.
From that, he discovered many noble gases such as neon.
Krypton's main use was as a definition of a metre. For 23 years from 1960-1983, the official definition for a metre was 1,650,763.73 wavelengths of the orange-red emission of
Krypton-86 in a vacuum. This means that 1 metre was measured by the wavelength of a certain type of light emitted by Krypton-83 while in a vacuum. It replaced a metal rod kept in a
museum, and was replaced by the speed of light in 1983.
Krypton also had many light-related uses. Because it is inert, it is used in fluorescent bulbs, preventing the filament from corroding. Also, like many noble
gases, when charged, it released a bright, nicely coloured light, such as shown in the background.
Krypton has 7 naturally occurring isotopes, with atomic weights ranging from 78 to 86amu, of which 2 are radioactive - 78Kr and 81Kr.
Krypton-78 has a half life of nearly 1x1022 years (10,000,000,000,000,000,000,000 years) - so long, that it is effectively considered stable. It has the second
longest half-life of any isotopes where decay has been seen. Krypton-81 has a half life of around 230,000 years, and is used to find the age of things that is
hundreds of thousands of years old.