![]() In the early 1960s, however, krypton was found to react with the element fluorine when both are combined in an electrical-discharge tube at −183 ☌ (−297 ☏) the compound formed is krypton difluoride, KrF 2. For many years it was considered to be totally unreactive. Krypton is the lightest of the noble gases that form isolable chemical compounds in macroscopic amounts. After it has been stored a few days, krypton obtained by nuclear fission contains only one radioactive isotope, krypton-85, which has a half-life of 10.7 years, because all the other radioactive isotopes have half-lives of 3 hours or less. The longest-lived of these, krypton-81, has a half-life of 229,000 years. Krypton has isotopes of every mass number from 69 through 101 of these isotopes,25 are radioactive and are produced by fission of uranium and by other nuclear reactions. Natural krypton is a mixture of six stable isotopes: krypton-84 (56.99 percent), krypton-86 (17.28 percent), krypton-82 (11.59 percent), krypton-83 (11.5 percent), krypton-80 (2.29 percent), and krypton-78 (0.36 percent). (One metre equaled 1,650,763.73 times the wavelength of this line.) The wavelength of an orange-red component of light emitted by stable krypton-86, because of its extreme sharpness, served from 1960 to 1983 as the international standard for the metre. When a current of electricity is passed through a glass tube containing krypton at low pressure, a bluish white light is emitted. Krypton is named from the Greek word kryptos, “hidden.” Radioactive krypton-85 is useful for detecting leaks in sealed containers, with the escaping atoms detected by means of their radiation. Krypton is used in certain electric and fluorescent lamps and in a flashlamp employed in high-speed photography. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.Demystified Videos In Demystified, Britannica has all the answers to your burning questions. ![]() This Time in History In these videos, find out what happened this month (or any month!) in history. ![]()
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