4/17/2024 0 Comments Periodic table molar mass'The dates indicate the true age of the minerals only if the rocks have not been subsequently altered (see rubidium–strontium dating). If the initial amount of Sr is known or can be extrapolated, then the age can be determined by measurement of the Rb and Sr concentrations and of the 87Sr/ 86Sr ratio. The highest ratios (10 or more) occur in pegmatites. Hence, the Rb/Sr ratio in residual magma may increase over time, and the progressing differentiation results in rocks with elevated Rb/Sr ratios. During fractional crystallization, Sr tends to concentrate in plagioclase, leaving Rb in the liquid phase. Rb has been used extensively in dating rocks 87Rb beta decays to stable 87Sr. It readily substitutes for potassium in minerals, and is therefore fairly widespread. Rubidium-87 has a half-life of 48.8 ×10 9 years, which is more than three times the age of the universe of (13.799 ☐.021) ×10 9 years, making it a primordial nuclide. Thirty additional rubidium isotopes have been synthesized with half-lives of less than 3 months most are highly radioactive and have few uses. Natural rubidium is radioactive, with specific activity of about 670 Bq/g, enough to significantly expose a photographic film in 110 days. Isotopes Īlthough rubidium is monoisotopic, rubidium in the Earth's crust is composed of two isotopes: the stable 85Rb (72.2%) and the radioactive 87Rb (27.8%). Rubidium forms salts with halogens, producing rubidium fluoride, rubidium chloride, rubidium bromide, and rubidium iodide. Rubidium forms a number of oxides when exposed to air, including rubidium monoxide (Rb 2O), Rb 6O, and Rb 9O 2 rubidium in excess oxygen gives the superoxide RbO 2. Rubidium silver iodide (RbAg 4I 5) has the highest room temperature conductivity of any known ionic crystal, a property exploited in thin film batteries and other applications. Other common rubidium compounds are the corrosive rubidium hydroxide (RbOH), the starting material for most rubidium-based chemical processes rubidium carbonate (Rb 2CO 3), used in some optical glasses, and rubidium copper sulfate, Rb 2SO 4♼uSO 4♶H 2O. Rubidium chloride (RbCl) is probably the most used rubidium compound: among several other chlorides, it is used to induce living cells to take up DNA it is also used as a biomarker, because in nature, it is found only in small quantities in living organisms and when present, replaces potassium. Rubidium and potassium show a very similar purple color in the flame test, and distinguishing the two elements requires more sophisticated analysis, such as spectroscopy. Rubidium has a very low ionization energy of only 406 kJ/mol. Rubidium crystals (silvery) compared to caesium crystals (golden) It forms amalgams with mercury and alloys with gold, iron, caesium, sodium, and potassium, but not lithium (even though rubidium and lithium are in the same group). Rubidium has also been reported to ignite spontaneously in air. As with potassium (which is slightly less reactive) and caesium (which is slightly more reactive), this reaction is usually vigorous enough to ignite the hydrogen gas it produces. Like other alkali metals, rubidium metal reacts violently with water. It is the second most electropositive of the stable alkali metals and melts at a temperature of 39.3 ☌ (102.7 ☏). Rubidium is a very soft, ductile, silvery-white metal. However, rubidium ions have similar properties and the same charge as potassium ions, and are actively taken up and treated by animal cells in similar ways.Ĭharacteristics Partially molten rubidium metal in an ampoule Rubidium is not a known nutrient for any living organisms. Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms. Rubidium's compounds have various chemical and electronic applications. The name comes from the Latin word rubidus, meaning deep red, the color of its emission spectrum. German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 by the newly developed technique, flame spectroscopy. On Earth, natural rubidium comprises two isotopes: 72% is a stable isotope 85Rb, and 28% is slightly radioactive 87Rb, with a half-life of 48.8 billion years-more than three times as long as the estimated age of the universe. Rubidium is the first alkali metal in the group to have a density higher than water. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is a chemical element it has symbol Rb and atomic number 37.
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