Rubidium (Rb) is a soft, silvery-white metallic element, classified as an alkali metal in Group 1 of the periodic table. It has an atomic number of 37. This highly reactive metal readily oxidizes upon exposure to air and reacts vigorously with water. Rubidium also possesses a low melting point, allowing it to become liquid at temperatures slightly above room temperature.
The Discovery Location and Its Pioneers
The discovery of rubidium took place in 1861 at the University of Heidelberg in Germany. This discovery resulted from a collaborative effort between two prominent German scientists, Robert Bunsen and Gustav Kirchhoff. Bunsen, a chemist, was recognized for his work on spectroscopy and gas analysis, while Kirchhoff, a physicist, was instrumental in developing the theoretical foundations of spectroscopy.
Their productive partnership at Heidelberg combined their expertise to pioneer new methods of chemical analysis. Their laboratory in Heidelberg became a center for groundbreaking research in analytical chemistry and physics.
It was within this environment that they focused on the detailed analysis of mineral samples. Their 1861 work involved examining lepidolite, a type of mica, and various mineral waters. This meticulous investigation laid the groundwork for the identification of previously unknown elements.
Unveiling Rubidium: The Spectroscopic Breakthrough
Rubidium’s identification was made possible through spectroscopy, a technique analyzing light emitted or absorbed by substances. When elements are heated, they emit light at specific wavelengths, creating unique spectral “fingerprints.” Spectroscopy passes this light through a prism to separate it into component colors, revealing distinct lines for each element.
Bunsen and Kirchhoff were pioneers in developing and refining the flame spectroscope. They applied this new analytical tool to residues obtained from large quantities of mineral waters, including those from Dürkheim. When these residues were heated in a flame, the light produced was analyzed through their spectroscope.
During this process, they observed distinct spectral lines that did not match any known elements. Among these observations were two prominent deep red lines, which indicated the presence of a new, undiscovered element. Rubidium was one of two new elements, the other being cesium, that Bunsen and Kirchhoff successfully identified using this groundbreaking spectroscopic method.
The Element’s Name and Early Significance
The name “rubidium” derived from the visual evidence observed during its spectroscopic discovery. The scientists chose the name from the Latin word “rubidus,” which means “deepest red.” This referred to the two prominent deep red spectral lines, the element’s unique spectroscopic signature.
The discovery of rubidium, alongside cesium, marked a significant moment in the history of chemistry. It confirmed a new element and demonstrated spectroscopy’s immense utility and precision for chemical analysis. This method allowed for the identification of elements present in even minute quantities within complex mixtures.
Its immediate significance was profound, validating a powerful new analytical technique. Furthermore, rubidium was quickly recognized as a new member of the alkali metal family, fitting into the emerging understanding of elemental classifications based on their chemical properties. Its discovery broadened the known scope of the periodic table and contributed to the foundational knowledge of elemental composition.