Krypton belongs to the family known as the noble gases. This family also includes helium, neon, argon, xenon and radon. All are considered nonreactive, nonmetallic elements and have eight valence electrons.
Krypton was first discovered by Sir William Ramsay and Morris Travers on May 30, 1898. It has an atomic symbol Kr and atomic number 36. Due to the high cost of isolating krypton, the element has few practical uses. It is used in certain types of high-speed photography. As it is one of the noble gases, krypton was thought to be inert and unable to form compounds. Krypton does have the ability to form a few compounds, including Krypton difluoride.