Rubidium was discovered (1861) spectroscopically by German scientists Robert Bunsen and Gustav Kirchhoff and named after the two prominent red lines of its spectrum. Rubidium and cesium often occur together in nature. Rubidium, however, is more widely scattered and seldom forms a natural mineral; it is found only as an impurity in other minerals, ranging in content up to 5 percent in such minerals as lepidolite, pollucite, and carnallite. The primary difficulty associated with the production of pure rubidium is that it is always found together with cesium in nature and is also mixed with other alkali metals. Because these elements are very similar chemically, their separation presented numerous problems before the advent of ion-exchange methods and ion-specific complexing agents such as crown ethers. Once pure salts have been prepared, it is a straightforward task to convert them to the free metal. This can be done by electrolysis of the fused cyanide or by reduction with calcium or sodium followed by fractional distillation. Properties
Rubidium is an alkali metal in group IA of the periodic table with atomic number 37, an atomic weight of 85.47, and a density of 1.53 Mg/m3. Its melting point is 38.9 °C, and it boils at 688 °C. Its atomic radius is 0.248 nm and the (+1) ionic radius is 0.148 nm. Number of p+ n° and e-
Rubidium has a number of protons of 37, neutrons 48 and electrons 37. Uses and compounds
There are relatively few commercial uses for rubidium or its compounds. Rubidium is used to make atomic clocks. But these clocks are used only for very specialized purposes where very precise time-keeping is important. Rubidium is also used to make photocells. A photocell is a device for converting light energy into electrical energy. But other members of the alkali family are still preferred for this application.
Alchemists in the early middle Ages knew about some barium minerals. Smooth pebble-like...