Rubidium (Rb)
Rubidium (Rb) is a chemical element with the atomic number 37, belonging to Group IA of the periodic table. It is a soft, silver-white metal that is primarily sourced from minerals containing potassium, with notable deposits in regions such as Maine and South Dakota, as well as internationally in Canada, Afghanistan, and Chile. Despite its relatively common occurrence in the Earth's crust, rubidium is typically found in low concentrations, making extraction challenging and limiting its industrial applications.
Rubidium's most significant uses include its role in photoelectric cells, where it generates electric current upon exposure to light, and in highly accurate atomic clocks, which are vital for global positioning systems. Additionally, the radioactive isotope rubidium-87 is utilized in geological dating, helping to determine the ages of ancient rocks and minerals. Discovered in 1861 by Robert Bunsen and Gustav Kirchhoff, rubidium's practical applications have expanded notably with advancements in electronics and medical technologies such as positron emission tomography (PET). Overall, rubidium plays a crucial role in both scientific research and various technological applications.
Rubidium (Rb)
Where Found
Rubidium is widely distributed in the Earth’s crust in moderate amounts. Although it is more common than lead, copper, or zinc, it is never found in concentrations of more than a few percentage points. The main sources of rubidium are various minerals containing potassium that are found worldwide. It can be found in Maine and South Dakota, in evaporites from other states, and in pegmatite sources in Canada, Afghanistan, Namibia, Peru, Zambia, and elsewhere. brine and evaporite sources are located in Chile, China, France, and Germany.
Primary Uses
Rubidium is used in photoelectric cells and other electronic devices. The radioactive isotope of rubidium is used to measure the ages of extremely old rock samples. Rubidium is also increasingly used as an atomic clock for global positioning satellites.
Technical Definition
Rubidium (abbreviated Rb), atomic number 37, belongs to Group IA of the periodic table of the elements and resembles cesium in its chemical and physical properties. It has two naturally occurring isotopes and an average atomic weight of 85.47. Pure rubidium is a soft, silver-white metal. Its density is 1.53 grams per cubic centimeter; it has a melting point of 39° Celsius and a boiling point of 688° Celsius.
Description, Distribution, and Forms
Rubidium is a widely distributed element resembling cesium. It occurs as oxides in various minerals that contain potassium in concentrations ranging from less than 1 percent to about 5 percent. Because rubidium never occurs in higher concentrations and is difficult to extract, its industrial uses are limited. However, the radioactive isotope of rubidium is used to determine the age of rocks, minerals, and meteorites.
History
Rubidium was discovered in 1861 by the German chemist Robert Bunsen and the German physicistGustav Robert Kirchhoff. Because rubidium was difficult to obtain, it had little practical use until the second half of the twentieth century, when the electronics industry developed.
Obtaining rubidium
Rubidium compounds may be obtained from various potassium ores in a number of ways. These procedures all require a complex series of chemical reactions. In general, the first step is to obtain compounds of potassium, rubidium, and cesium from the ore. The potassium compound, which makes up the majority of this mixture, is separated from the others. The cesium is then separated from the rubidium. These separations generally involve forming compounds that have different solubilities. The compounds are dissolved, and the least soluble one is crystallized while the others remain in solution.
Once a rubidium compound is obtained, it can be transformed into free rubidium metal by various methods. One common procedure involves mixing rubidium chloride with calcium and heating the mixture to between 700° and 800° Celsius. A method often used in the production of photoelectric cells involves mixing rubidium chromate with zirconium and heating the mixture to about 700° Celsius. Rubidium may also be obtained by heating rubidium azide to about 500° Celsius in a vacuum.
Uses of Rubidium
The most important use for rubidium is in photoelectric cells. Rubidium releases electrons when it is exposed to light, resulting in an electric current. Another use is based on the fact that the naturally occurring radioactive isotope rubidium 87 decays into strontium 87, with a half-life of sixty-three billion years. By measuring the amount of strontium 87 present, scientists can measure the age of rocks. The rubidium atomic clock is extremely accurate, making satellite and other high-tech applications significant. Finally, rubidium 82 is used in positron emission tomography (PET); hence, its applications have advanced with the use of PET medical technology.
Bibliography
WebElements.