Rubidium

Rubidium (IPA: /ruːˈbɪdiəm, rəˈbɪdiəm/) is a chemical element in the periodic table that has the symbol Rb and atomic number 37. Rb is a soft, silvery-white metallic element of the alkali metal group. Rb-87, a naturally occurring isotope, is (slightly) radioactive. Rubidium is very soft and highly reactive, with properties similar to other elements in group 1, like rapid oxidation in air.