Bunsen and Kirchhoff told how they named the new element The magnificent dark red color of these rays of the new alkali metal led us to give this element the name rubidium and the symbol Rb from ‘rubidium’, which, with the ancients, served to designate the deepest red. Rubidium was discovered in 1861 by Bunsen and Kirchhoff in the mineral lepidolite by use of the spectroscope. The element is much more abundant than was thought several years ago. It is now considered to be the 16th most abundant element in the earth's crust. Rubidium occurs in pollucite, carnallite, leucite, and zinnwaldite, which contains traces up to 1% in the form of oxide. It is soft silvery white metallic element of the alkali group and is the second most electropositive and alkaline element. It ignites spontaneously in air and reacts violently in water, setting fire to the liberated hydrogen. It colors a flame yellowish violet. It must be kept under a dry mineral oil or in a vacuum or inert atmosphere.Cesium was discovered by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, German chemists, in 1860 through the spectroscopic analysis of Durkheim mineral water. They named cesium after the blue lines they observed in its spectrum. Today, cesium is primarily obtained from the mineral pollucite (CsAlSi2O6). Obtaining pure cesium is difficult since cesium ores are frequently contaminated with rubidium, an element that is chemically similar to cesium. To obtain pure cesium, cesium and rubidium ores are crushed and heated with sodium metal to 650°C, forming an alloy that can then be separated with a process known as fractional distillation. Metallic cesium is too reactive to easily handle and is usually sold in the form of cesium azide (CsN3). Cesium is recovered from cesium azide by heating it.Cesium has the second lowest melting point of all metallic elements, which limits its uses. Cesium readily combines with oxygen and is used as a getter, a material that combines with and removes trace...