Rubidium was discovered in 1861. It belongs to the alkali metals group of the periodic table. It is an abundant and highly reactive metal.
History and Discovery
Rubidium was discovered by Gustav Kirchhoff and Robert Bunsen in 1861. They used the technique known as flame spectroscopy to isolate the new element. The name rubidium has been derived from Latin word rubidus, that means deep red. It was given to the element as it emitted bright red lines in its emission spectrum [1]. The radioactivity of rubidium was discovered in 1908. The discoverers of Bose-Einstein condensate in 1995 used rubidium-87 and were awarded the Nobel prize in Physics in 2001 [2].
Rubidium
| Periodic Table Classification | Group 1 Period 5 |
|---|---|
| State at 20C | Solid |
| Color | Grey white |
| Electron Configuration | [Kr] 5s1 |
| Electron Number | 37 |
| Proton Number | 37 |
| Electron Shell | 2, 8, 18, 8, 1 |
| Density | 1.63 g.cm-3 at 20°C |
| Atomic number | 37 |
| Atomic Mass | 85.47 g.mol -1 |
| Electronegativity according to Pauling | 0.82 |
Occurrence
Rubidium is an abundant element and is ranked as the twenty-third most abundant element in the Earth’s crust [3]. In mostly occurs in the form of minerals, including carnallite, leucite, zinnwaldite and pollucite. The commercial production of rubidium is carried out from lepidolite, which contains up to 3.5% of rubidium [4]. Various minerals of potassium and potassium chlorides also contain significant amounts of rubidium. Rubidium is also present in the sea water, with a concentration of 125 µg/L which is much lower as compared to potassium. The largest producers of rubidium which have large deposits of the metal include Canada and Italy [5].
Physical Characteristics
Rubidium is silvery-white metal. It belongs to the alkali metal group of elements and is soft in nature. Rubidium is ductile metal and used for various purposes. It has a melting point of 39.3°C and have a low density, 1.532 g/cm3.
Chemical Characteristics
Rubidium is a very reactive metal. It undergoes rapid oxidation in the presence of air. Rubidium burns with a purplish flame like potassium. It has high electropositive values and is ranked second among the stable alkali metal. Rubidium reacts vigorously with water and can lead to the ignition of hydrogen gas that is produced during the reaction. It also undergoes spontaneous ignition when exposed to air. It forms alloys with iron, gold, sodium and potassium and forms amalgams with mercury. The ionization energy of rubidium is very low, 406 kJ/mol. The most common and widely used compound of rubidium is rubidium chloride (RbCl). There are various oxides of rubidium, and forms superoxide when excess amount of oxygen is present.
Significance and Uses
- Rubidium is widely used in the manufacturing of electronic devices.
- Rubidium is used to make purple colored fireworks.
- It is used to make thermoelectric generators.
- Rubidium is used in making photocells, oscillators and vacuum tubes.
- Rubidium is used in the manufacturing of special type of glass.
- Rubidium-82 is used for medical purposes for the diagnosis of various diseases, such as myocardial perfusion and detection of brain tumors.
Health Effects
Rubidium is a non-toxic metal. Rubidium has no biological role. However, the similarity of charge between rubidium and potassium ions makes it taken up by the cells in similar ways as potassium. Due to its vigorous reaction with water and its ability to spontaneously catch fire, the handling and storage of rubidium is quite challenging. Rubidium can be taken up by cells of the body, but these ions are not poisonous. The biological half-life of rubidium is around 50 days.
Isotopes of Rubidium
There are two naturally occurring isotopes in rubidium, rubidium-85 is the stable and more abundant isotope, while rubidium-87 is the radioactive isotope. Rubidium-87 has a half-life of around 49 billion years and is considered as a primordial nuclide. There are twenty-four artificial radioactive isotopes of rubidium, which have a half-life of less than 90 days [6].
REFERENCES
[1]. Weeks, Mary Elvira (1932). “The discovery of the elements. XIII. Some spectroscopic discoveries”. Journal of Chemical Education. 9 (8): 1413–1434. Bibcode:1932JChEd…9.1413W. doi:10.1021/ed009p1413.
[2]. Levi, Barbara Goss (2001). “Cornell, Ketterle, and Wieman Share Nobel Prize for Bose-Einstein Condensates”. Physics Today. Physics Today online. 54 (12): 14. Bibcode:2001PhT….54l..14L. doi:10.1063/1.1445529.
[3]. Butterman, William C.; Brooks, William E.; Reese, Jr., Robert G. (2003). “Mineral Commodity Profile: Rubidium” (PDF). United States Geological Survey. Retrieved 2010-12-04
[4]. Wise, M. A. (1995). “Trace element chemistry of lithium-rich micas from rare-element granitic pegmatites”. Mineralogy and Petrology. 55 (13): 203–215. Bibcode:1995MinPe..55..203W. doi:10.1007/BF01162588.
[5]. Teertstra, David K.; Cerny, Petr; Hawthorne, Frank C.; Pier, Julie; Wang, Lu-Min; Ewing, Rodney C. (1998). “Rubicline, a new feldspar from San Piero in Campo, Elba, Italy”. American Mineralogist. 83 (11–12 Part 1): 1335–1339. Bibcode:1998AmMin..83.1335T. doi:10.2138/am-1998-11-1223.
[6]. Audi, Georges; Bersillon, O.; Blachot, J.; Wapstra, A. H. (2003). “The NUBASE Evaluation of Nuclear and Decay Properties”. Nuclear Physics A. Atomic Mass Data Center. 729 (1): 3–128. Bibcode:2003NuPhA.729….3A. doi:10.1016/j.nuclphysa.2003.11.001.