Element Krypton, Kr, Noble Gas

After Sir William Ramsay's discovery of argon and helium a question arose, how to allocate elements in the periodical system. Ramsay used Mendeleev's idea and put the symbols of new-discovered gases close-by to the other elements in the order of growing atomic masses. It had become clearly seen that an empty space appeared between helium and argon. Some more voids had been revealed below argon between bromine and rubidium as well as between caesium and iodine. It had become obvious that inert gases also called Noble Gass belonged to a separate group in the periodic system. In autumn of 1897 Ramsay, the President of the Chemistry Section of the British Association for the Advancement of Science made a report on the Association meeting in Toronto meeting about the undiscovered gas and its hypothetical place in the periodical system. The report inspired researcher to start to search the not yet discovered gas in mineral waters. However Ramsay himself had been credited as the discoverer of the new element along with his assistant, Morris Travers in residue left from evaporating nearly all components of liquid air. It was named krypton, from Greek κρυπτον, krypton meaning "hidden thing" or "secret one".

Krypton abundance in air is about 1.14x10^-4% by vol., total deposits 5.3x10¹²m³. 1 m³ of air contains 1 sm³ of krypton.