Rubidium unlike other Alkali metals will not float on water due to its high density. Rubidium was discovered in 1861 by German chemists Robert Bunsen and Gustav Kirchhoff using spectroscopy. They analysed the mineral lepidolite and witnessed a bright red emission line. Rubidium is named after the Latin ‘rubidus’ which means deep red. Rubidium has a number of uses, primarily in fireworks. Rubidium’s isotopes exhibit radioactive activity and Rb 87 is commonly sed in laser cooling and also in atomic clocks. It is located in Group 1, an Alkali metal. It has a melting point of 39.9°c and a boiling point of 688°c.
R. Bunsen, G. Kirchoff