The chemical element Kr is also known as Krypton. It is a gas that is part of the noble gas group on the periodic table. Its atomic number is 36 and it has the symbol Kr. Krypton is odorless, colorless and non-toxic. Some synonyms for the element Krypton include noble gas, rare gas, and inert gas. These terms all describe the element's characteristics of being unreactive and stable. Krypton is often used in lighting, particularly in fluorescent lamps and photographic flashes. It is also used in high-speed photography, as well as in gas mixtures used in nuclear reactors.