Krypton, << KRIHP ton, >> is a chemical element that makes up only about one-millionth of Earth’s atmosphere. The British chemists Sir William Ramsay and Morris W. Travers discovered it in 1898. It was named krypton for the Greek word which means the hidden one. Most fluorescent lamps are filled with a mixture of krypton and argon. Krypton is also used in certain electronic tubes, and in luminous sign tubes where a greenish-yellow color is desired.
Krypton is a colorless, odorless, tasteless gas. It does not react readily with other substances and is classed as a noble gas . Its symbol is Kr. The element has an atomic number (number of protons in its nucleus) of 36. Its relative atomic mass is 83.80. An element’s relative atomic mass equals its mass (amount of matter) divided by 1/12 of the mass of carbon 12, the most abundant form of carbon. Krypton can be condensed to a liquid that boils at –152.3 °C and freezes at –156.6 °C. It is obtained in the manufacture of liquid air. For information on the position of krypton on the periodic table, see the article Periodic table .
