Rubidium was discovered by two German scientists, of the University of Heidelberg: [chemist], Robert W. (Wilhelm) Bunsen & [physicist] Gustav R. (Robert) Kirchhoff, in 1861. The discovery wasn’t intentional, but in fact accidental. The science duo had been investigating mineral lepidolite, a form of mica consisting of the elements lithium, potassium and a few traces of rubidium, which was not known to be present.
They were interested in lepidolite because of a rare reaction with the mineral. When thrown into flaming coals, the mineral would froth up and harden like glass. The metal was dissolved in acid and precipitated the potassium, which was in the metal and was carried down by a heavier alkali metal. Bunsen and Kirchhoff carefully washed the precipitate with scorching water and removed the more dissolved potassium segment. That was when they realized they had discovered a new element due to the atomic arrangement of what was left. A fragment of pure rubidium was produced in 1928.
Rubidium has five valence shells and 48 neutrons. It had an atomic mass of 85.36 but is now known to be 85.47. Rubidium is a soft, silvery-white alkali metal. It has a melting point of 38.89 °C and a boiling point of 688 °C. It has a density of 1.532 g/cm3. Rubidium has such a low melting point it could melt in your hand.
Rubidium is very reactive and ignites in the air due to the nitrogen and oxygen around us. It also reacts violently with water. Rubidium is not known to be toxic and has a pH of 14, which categorizes it as a strong alkali.
There are two naturally occurring isotopes that currently exist: Rubidium- 85 and Rubidium- 87, which is radioactive. Fireworks come in all sorts of different colors and rubidium is used to make purple fireworks. Also Rubidium silver iodide, has the highest room temperature conductivity (electricity) of any known ionic crystal, consists of one rubidium atom, four silver atoms and five iodine atoms. Rubidium is most commonly produced by passing an electrical current through molten (melted) rubidium chloride.
Rubidium does not have a lot of common uses, but here are some that I could find online. The element is used to make:
- Purple fireworks
- Special types of glass
- To make superoxide ions
- Space vehicles (ion engines)
- “Getter(s)” in vacuum tubes
- Photo cells
- Catalyst
- Working fluid in vapor turbines
- To make atomic clocks
- Thin film batteries