Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Rubidium is a chemical element with the symbol Rb and atomic number 37. Rb is a soft, silvery-white metallic element of the alkali metal group. Rubidium is very soft and highly reactive, with properties similar to other elements in group 1, such as very rapid oxidation in air. Its compounds have chemical and electronic applications. Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms.