Rubidium's atomic number is 37 and its symbol is Rb. It is a very soft, silvery-white metal in the alkali metal group, and it is the first in the group to have a density higher than water. Rubidium is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms. However, it cannot be stored under atmospheric oxygen, as a highly exothermic reaction will ensue, sometimes even resulting in the metal catching fire.

Rubidium had minimal industrial value before the 1920s. Since then, the most important use of rubidium is research and development, primarily in chemical and electronic applications. Currently, Rubidium compounds are sometimes used in fireworks to give them a purple color, working fluid in vapor turbines, as a getter in vacuum tubes, and as a photocell component.

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