Template:Infobox rubidiumRubidium (Template:PronEng, Template:Respell) is a chemical element with the symbol Rb and atomic number 37. Rb is a soft, silvery-white metallic element of the alkali metal group.

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JACKSON IS COOL NOT LIKE THIS FAKE ELEMENThas a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms.

Rubidium is not known to be necessary for any living organisms. However, like caesium, rubidium ions are handled by living organisms in a manner similar to potassium: it is actively taken up by plants and by living animals' cells.

Rubidium has one stable isotope,<sup>85</sup>Rb. The isotope <sup>87</sup>Rb which composes almost 28% of naturally occurring rubidium is slightly radioactive, with a half-life of 49 billion years—more than three times longer than the estimated age of the universe.

== Characteristics ==Rubidium is the second most electropositive of the stable alkali elements and liquefies at a high ambient temperature<!--clarify me please-->, 39.3 °C. Like other group 1 elements this metal reacts violently in water. In common with potassium and caesium this reaction is usually vigorous enough to ignite the liberated hydrogen. Rubidium has also been reported to ignite spontaneously in air.  Also like other alkali metals, it forms amalgams with mercury and it can form alloys with gold, caesium, sodium, and potassium. The element gives a reddish-violet color to a flame, hence its name.

== History ==
Rubidium (L rubidus, deepest red) was discovered in 1861 by Robert Bunsen and Gustav Kirchhoff in the mineral lepidolite through the use of a spectroscope.<ref>{{cite journal
 | title = Chemische Analyse durch Spectralbeobachtungen
 | pages = 337–381
 | author = G. Kirchhoff, R. Bunsen
 | doi = 10.1002/andp.18611890702
 | journal = Annalen der Physik und Chemie
 | volume = 189
 | issue = 7 | year = 1861}}</ref> The extraction of 150 kg of lepidolite yielded only a few grams for analysis. The first rubidium metal was produced by the reaction of rubidium chloride with potassium by Bunsen.

== Occurrence ==Rubidium is about the twenty-third<ref></ref> most abundant element in the Earth's crust, roughly as abundant as zinc and rather more common than copper. It occurs naturally in the minerals leucite, pollucite, carnallite and zinnwaldite, which contains traces of up to 1% of its oxide. Lepidolite contains 1.5% rubidium and this is the commercial source of the element. Some potassium minerals and potassium chlorides  also contain the element in commercially significant amounts. One notable source is also in the extensive deposits of pollucite at Bernic Lake, Manitoba (also a source of the related element caesium).

Rubidium metal can be produced by reducing rubidium chloride with calcium among other methods.  In 1997 the cost of this metal in small quantities was about US$25/gram.

== Isotopes ==

Main article: Isotopes of rubidium
There are 26 isotopes of rubidium known with naturally occurring rubidium being composed of just two isotopes; Rb-85 (72.2%) and the radioactive Rb-87 (27.8%). Natural rubidium is radioactive with specific activity of about 670 Bq/g, enough to fog photographic film in approximately 30 to 60 days.

Rb-87 has a half-life of 4.88×1010 years. It readily substitutes for potassium in minerals, and is therefore fairly widespread. Rb has been used extensively in dating rocks; Rb-87 decays to stable strontium-87 by emission of a negative beta particle. During fractional crystallization, Sr tends to become concentrated in plagioclase, leaving Rb in the liquid phase. Hence, the Rb/Sr ratio in residual magma may increase over time, resulting in rocks with increasing Rb/Sr ratios with increasing differentiation. Highest ratios (10 or higher) occur in pegmatites. If the initial amount of Sr is known or can be extrapolated, the age can be determined by measurement of the Rb and Sr concentrations and the Sr-87/Sr-86 ratio. The dates indicate the true age of the minerals only if the rocks have not been subsequently altered. See Rubidium-Strontium dating for a more detailed discussion.

== Uses and applications ==Rubidium had minimal industrial use until the 1930s. Historically, the most important use for rubidium has been in research and development, primarily in chemical and electronic applications.

In 1999 rubidium-87 was used to make a Bose-Einstein condensate<ref>Bose-Einstein Condensation. World of Physics on Bose-Einstein Condensation. BookRags . Retrieved on 2008-01-26.</ref>, for which the discoverers won the 2001 Nobel Prize in Physics<ref>Levi, Barbara Goss (2001). Cornell, Ketterle, and Wieman Share Nobel Prize for Bose-Einstein Condensates. Search & Discovery. Physics Today online  . Retrieved on 2008-01-26.</ref>.

Rubidium is easily ionized, so it has been considered for use in ion engines for space vehicles (but caesium and xenon are more efficient for this purpose).

Rubidium compounds are sometimes used in fireworks to give them a purple color.

RbAg<sub>4</sub>I<sub>5</sub> has the highest room temperature conductivity of any known ionic crystal. This property could be useful in thin film batteries and in other applications.<ref>Bradley, J. N. (1967). "Relationship of structure and ionic mobility in solid MAg4I5". Trans. Faraday Soc. 63: 2516. DOI:10.1039/TF9676302516.</ref>

Rubidium has also been considered for use in a thermoelectric generator using the magnetohydrodynamic principle, where rubidium ions are formed by heat at high temperature and passed through a magnetic field. These conduct electricity and act like an armature of a generator thereby generating an electric current.

Rubidium, particularly <sup>87</sup>Rb, in the form of vapor, is one of the most commonly used atomic species employed for laser cooling and Bose-Einstein condensation. Its desirable features for this application include the ready availability of inexpensive diode laser light at the relevant wavelength, and the moderate temperatures required to obtain substantial vapor pressures.

Rubidium has been used for polarizing <sup>3</sup>He (that is, producing volumes of magnetized <sup>3</sup>He gas, with the nuclear spins aligned toward a particular direction in space, rather than randomly). Rubidium vapor is optically pumped by a laser and the polarized Rb polarizes <sup>3</sup>He by the hyperfine interaction.<ref>Gentile, T.R. et al.. "Polarized 3He spin filters for slow neutron physics". Journal of Research of the National Institute of Standards and Technology 100: 299. </ref> Spin-polarized <sup>3</sup>He cells are becoming popular for neutron polarization measurements and for producing polarized neutron beams for other purposes.<ref>Neutron spin filters based on polarized helium-3. NIST Center for Neutron Research 2002 Annual Report. </ref>

Rubidium is the primary compound used in secondary frequency references (Rubidium Oscillators) to maintain frequency accuracy in cell site transmitters and other electronic transmitting, networking and test equipment. Rubidium references are often used with GPS to produce a "Primary Frequency Standard" that has greater accuracy but is less expensive than Cesium standards. Rubidium references such as the LPRO series from Datum were mass-produced for the Telecom industry and are now selling for under one hundred dollars on the secondary market. The general life expectancy is 10 years or better for most designs.

Other potential or current uses of rubidium include:
*A working fluid in vapor turbines.
*A getter in vacuum tubes.
*A photocell component.
*The resonant element in atomic clocks. This is due to the hyperfine structure of rubidium's energy levels.
*An ingredient in special types of glass.
*The production of superoxide by burning in oxygen.
*The study of potassium ion channels in biology.
*Rubidium is used to locate brain tumours, due to its slight radioactivity. <ref></ref>*Rubidium vapor has been used to make atomic magnetometers.  <sup>87</sup>Rb is currently being used, with other alkali metals, in the development of spin-exchange relaxation-free (SERF) magnetometers.<ref>Li, Zhimin et al. (2006). "Parametric modulation of an atomic magnetometer". Applied Physics Letters 89: 134105. DOI:10.1063/1.2357553.</ref>

Template:MoreRubidium chloride is probably the most-used rubidium compound; it is used in biochemistry to induce cells to take up DNA, and as a biomarker since it is readily taken up to replace potassium, and does not normally occur in living organisms. Rubidium hydroxide is the starting material for most rubidium-based chemical processes; rubidium carbonate is used in some optical glasses.

Rubidium has a number of oxides, including Rb<sub>6</sub>O and Rb<sub>9</sub>O<sub>2</sub> which appear if rubidium metal is left exposed to air; the final product of reacting with oxygen is the superoxide RbO<sub>2</sub>. Rubidium forms salts with most anions. Some common rubidium compounds are rubidium chloride (RbCl), rubidium monoxide (Rb<sub>2</sub>O) and rubidium copper sulfate Rb<sub>2</sub>SO<sub>4</sub>·CuSO<sub>4</sub>·6H<sub>2</sub>O). A compound of rubidium, silver and iodine, RbAg<sub>4</sub>I<sub>5</sub>, has interesting electrical characteristics and might be useful in thin film batteries.<ref>Smart, Lesley  (1995). "Solid state chemistry: an introduction": 176–177.</ref>

==Precautions==Rubidium reacts violently with water and can cause fires. To ensure both health and safety and purity, this element must be kept under a dry mineral oil, and in practice is usually sealed in glass ampules in an inert atmosphere. Rubidium forms peroxides on exposure to even air diffusing into oil, and is thus subject to some of the same peroxide precautions as storage of metallic potassium.

== Biological effects ==Rubidium, like sodium and potassium, is almost always in its +1 oxidation state when dissolved in water, and this includes all biological systems. The human body tends to treat Rb<sup>+</sup> ions as if they were potassium ions, and therefore concentrates rubidium in the body's intracellular fluid (i.e., inside cells). The ions are not particularly toxic, and are relatively quickly removed in the sweat and urine. As a result of changes in the blood brain barrier in brain tumors, rubidium collects more in brain tumors than normal brain tissue, allowing short-lived radioisotopes of rubidium to be used in nuclear medicine to locate and image brain tumors.

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*Los Alamos National Laboratory – Rubidium
*Louis Meites, Handbook of Analytical Chemistry (New York: McGraw-Hill Book Company, 1963)*Daniel A. Steck. Rubidium-87 D Line Data. Los Alamos National Laboratory (technical report LA-UR-03-8638).

==External links==
Template:Wiktionary* – Rubidium

Template:Compact periodic tableTemplate:Rubidium compounds




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