Rubidium is a chemical element with symbol Rb and atomic number 37. Rubidium is a incredibly soft, silvery-white metallic element of the alkali metal group. Rubidium metal shares similarities to Potassium metal and Cesium metal in physical apperance, such as softness and conductivity[6]. Rubidium cannot be stored under atmospheric Oxygen as a highly exothermic reaction will ensue, sometimes even resulting in the metal catching fire[7].

Rubidium is the first alkali metal in the group to have a density higher than that of Oxidane(water), so it sinks unlike the metals above it in the group. Rubidium has a standard atomic weight of 85.4678. On Earth, natural rubidium comprises two isotopes: 72% is the stable isotope, 85Rb; 28% is the slightly radioactive 87Rb, with a half-life of 49 billion years—more than three times longer than the estimated age of the universe.

German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 by the newly developed technique, flame spectroscopy. The name comes from the Latin word rubidus, meaning deep red, the color of its emission spectrum. Rubidium's compounds have various chemical and electronic applications. Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms. Rubidium is not a known nutrient for any living organisms. However, rubidium ions have the same charge as potassium ions, and are actively taken up and treated by animal cells in similar ways.

Rubidium,  37Rb
Pronunciation/ruːˈbɪdiəm/ (roo-BID-ee-əm)
Appearancegrey white
Standard atomic weight Ar, std(Rb)85.4678(3)[1]
Rubidium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


Atomic number (Z)37
Groupgroup 1 (alkali metals)
Periodperiod 5
Element category  alkali metal
Electron configuration[Kr] 5s1
Electrons per shell
2, 8, 18, 8, 1
Physical properties
Phase at STPsolid
Melting point312.45 K ​(39.30 °C, ​102.74 °F)
Boiling point961 K ​(688 °C, ​1270 °F)
Density (near r.t.)1.532 g/cm3
when liquid (at m.p.)1.46 g/cm3
Triple point312.41 K, ​? kPa[2]
Critical point2093 K, 16 MPa (extrapolated)[2]
Heat of fusion2.19 kJ/mol
Heat of vaporization69 kJ/mol
Molar heat capacity31.060 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 434 486 552 641 769 958
Atomic properties
Oxidation states−1, +1 (a strongly basic oxide)
ElectronegativityPauling scale: 0.82
Ionization energies
  • 1st: 403 kJ/mol
  • 2nd: 2632.1 kJ/mol
  • 3rd: 3859.4 kJ/mol
Atomic radiusempirical: 248 pm
Covalent radius220±9 pm
Van der Waals radius303 pm
Color lines in a spectral range
Spectral lines of rubidium
Other properties
Natural occurrenceprimordial
Crystal structurebody-centered cubic (bcc)
Body-centered cubic crystal structure for rubidium
Speed of sound thin rod1300 m/s (at 20 °C)
Thermal expansion90 µm/(m·K)[3] (at r.t.)
Thermal conductivity58.2 W/(m·K)
Electrical resistivity128 nΩ·m (at 20 °C)
Magnetic orderingparamagnetic[4]
Magnetic susceptibility+17.0·10−6 cm3/mol (303 K)[5]
Young's modulus2.4 GPa
Bulk modulus2.5 GPa
Mohs hardness0.3
Brinell hardness0.216 MPa
CAS Number7440-17-7
DiscoveryRobert Bunsen and Gustav Kirchhoff (1861)
First isolationGeorge de Hevesy
Main isotopes of rubidium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
83Rb syn 86.2 d ε 83Kr
84Rb syn 32.9 d ε 84Kr
β+ 84Kr
β 84Sr
85Rb 72.17% stable
86Rb syn 18.7 d β 86Sr
87Rb 27.83% 4.9×1010 y β 87Sr


Partially molten rubidium metal in an ampoule

Rubidium is a very soft, ductile, silvery-white metal.[8] It is the second most electropositive of the stable alkali metals and melts at a temperature of 39.3 °C (102.7 °F). Like other alkali metals, rubidium metal reacts violently with water. 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. Rubidium has also been reported to ignite spontaneously in air.[8] 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).[9]

Rb&Cs crystals
Rubidium crystals (silvery) compared to caesium crystals (golden)

Rubidium has a very low ionization energy of only 406 kJ/mol.[10] 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.


Rb9O2 cluster

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. Other common rubidium compounds are the corrosive rubidium hydroxide (RbOH), the starting material for most rubidium-based chemical processes; rubidium carbonate (Rb2CO3), used in some optical glasses, and rubidium copper sulfate, Rb2SO4·CuSO4·6H2O. Rubidium silver iodide (RbAg4I5) has the highest room temperature conductivity of any known ionic crystal, a property exploited in thin film batteries and other applications.[11][12]

Rubidium forms a number of oxides when exposed to air, including rubidium monoxide (Rb2O), Rb6O, and Rb9O2; rubidium in excess oxygen gives the superoxide RbO2. Rubidium forms salts with halides, producing rubidium fluoride, rubidium chloride, rubidium bromide, and rubidium iodide.


Although 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%).[13] Natural rubidium is radioactive, with specific activity of about 670 Bq/g, enough to significantly expose a photographic film in 110 days.[14][15]

Twenty four additional rubidium isotopes have been synthesized with half-lives of less than 3 months; most are highly radioactive and have few uses.

Rubidium-87 has a half-life of 48.8×109 years, which is more than three times the age of the universe of (13.799±0.021)×109 years,[16] making it a primordial nuclide. It readily substitutes for potassium in minerals, and is therefore fairly widespread. Rb has been used extensively in dating rocks; 87Rb beta decays to stable 87Sr. During fractional crystallization, Sr tends to concentrate in plagioclase, leaving Rb in the liquid phase. Hence, the Rb/Sr ratio in residual magma may increase over time, and the progressing differentiation results in rocks with elevated Rb/Sr ratios. The highest ratios (10 or more) occur in pegmatites. 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 dates indicate the true age of the minerals only if the rocks have not been subsequently altered (see rubidium–strontium dating).[17][18]

Rubidium-82, one of the element's non-natural isotopes, is produced by electron-capture decay of strontium-82 with a half-life of 25.36 days. With a half-life of 76 seconds, rubidium-82 decays by positron emission to stable krypton-82.[13]


Rubidium is the twenty-third most abundant element in the Earth's crust, roughly as abundant as zinc and rather more common than copper.[19] It occurs naturally in the minerals leucite, pollucite, carnallite, and zinnwaldite, which contain as much as 1% rubidium oxide. Lepidolite contains between 0.3% and 3.5% rubidium, and is the commercial source of the element.[20] Some potassium minerals and potassium chlorides also contain the element in commercially significant quantities.[21]

Seawater contains an average of 125 µg/L of rubidium compared to the much higher value for potassium of 408 mg/L and the much lower value of 0.3 µg/L for caesium.[22]

Because of its large ionic radius, rubidium is one of the "incompatible elements."[23] During magma crystallization, rubidium is concentrated together with its heavier analogue caesium in the liquid phase and crystallizes last. Therefore, the largest deposits of rubidium and caesium are zone pegmatite ore bodies formed by this enrichment process. Because rubidium substitutes for potassium in the crystallization of magma, the enrichment is far less effective than that of caesium. Zone pegmatite ore bodies containing mineable quantities of caesium as pollucite or the lithium minerals lepidolite are also a source for rubidium as a by-product.[19]

Two notable sources of rubidium are the rich deposits of pollucite at Bernic Lake, Manitoba, Canada, and the rubicline ((Rb,K)AlSi3O8) found as impurities in pollucite on the Italian island of Elba, with a rubidium content of 17.5%.[24] Both of those deposits are also sources of caesium.


Although rubidium is more abundant in Earth's crust than caesium, the limited applications and the lack of a mineral rich in rubidium limits the production of rubidium compounds to 2 to 4 tonnes per year.[19] Several methods are available for separating potassium, rubidium, and caesium. The fractional crystallization of a rubidium and caesium alum (Cs,Rb)Al(SO4)2·12H2O yields after 30 subsequent steps pure rubidium alum. Two other methods are reported, the chlorostannate process and the ferrocyanide process.[19][25]

For several years in the 1950s and 1960s, a by-product of potassium production called Alkarb was a main source for rubidium. Alkarb contained 21% rubidium, with the rest being potassium and a small amount of caesium.[26] Today the largest producers of caesium, such as the Tanco Mine, Manitoba, Canada, produce rubidium as a by-product from pollucite.[19]

Die Flammenfärbung des Rubidium
Flame test for rubidium


Kirchhoff Bunsen Roscoe
Gustav Kirchhoff (left) and Robert Bunsen (center) discovered rubidium by spectroscopy. (Henry Enfield Roscoe is on the right side.)

Rubidium was discovered in 1861 by Robert Bunsen and Gustav Kirchhoff, in Heidelberg, Germany, in the mineral lepidolite through flame spectroscopy. Because of the bright red lines in its emission spectrum, they chose a name derived from the Latin word rubidus, meaning "deep red".[27][28]

Rubidium is a minor component in lepidolite. Kirchhoff and Bunsen processed 150 kg of a lepidolite containing only 0.24% rubidium oxide (Rb2O). Both potassium and rubidium form insoluble salts with chloroplatinic acid, but those salts show a slight difference in solubility in hot water. Therefore, the less-soluble rubidium hexachloroplatinate (Rb2PtCl6) could be obtained by fractional crystallization. After reduction of the hexachloroplatinate with hydrogen, the process yielded 0.51 grams of rubidium chloride for further studies. Bunsen and Kirchhoff began their first large-scale isolation of caesium and rubidium compounds with 44,000 litres (12,000 US gal) of mineral water, which yielded 7.3 grams of caesium chloride and 9.2 grams of rubidium chloride.[27][28] Rubidium was the second element, shortly after caesium, to be discovered by spectroscopy, just one year after the invention of the spectroscope by Bunsen and Kirchhoff.[29]

The two scientists used the rubidium chloride to estimate that the atomic weight of the new element was 85.36 (the currently accepted value is 85.47).[27] They tried to generate elemental rubidium by electrolysis of molten rubidium chloride, but instead of a metal, they obtained a blue homogeneous substance which "neither under the naked eye nor under the microscope showed the slightest trace of metallic substance." They presumed it was a subchloride (Rb
); however, the product was probably a colloidal mixture of the metal and rubidium chloride.[30] In a second attempt to produce metallic rubidium, Bunsen was able to reduce rubidium by heating charred rubidium tartrate. Although the distilled rubidium was pyrophoric, they were able to determine the density and the melting point. The quality of this research in the 1860s can be appraised by the fact that their determined density differs less than 0.1 g/cm3 and the melting point by less than 1 °C from the presently accepted values.[31]

The slight radioactivity of rubidium was discovered in 1908, but that was before the theory of isotopes was established in 1910, and the low level of activity (half-life greater than 1010 years) made interpretation complicated. The now proven decay of 87Rb to stable 87Sr through beta decay was still under discussion in the late 1940s.[32][33]

Rubidium had minimal industrial value before the 1920s.[34] Since then, the most important use of rubidium is research and development, primarily in chemical and electronic applications. In 1995, rubidium-87 was used to produce a Bose–Einstein condensate,[35] for which the discoverers, Eric Allin Cornell, Carl Edwin Wieman and Wolfgang Ketterle, won the 2001 Nobel Prize in Physics.[36]


Rubidium compounds are sometimes used in fireworks to give them a purple color.[37] Rubidium has also been considered for use in a thermoelectric generator using the magnetohydrodynamic principle, where hot rubidium ions are passed through a magnetic field.[38] These conduct electricity and act like an armature of a generator thereby generating an electric current. Rubidium, particularly vaporized 87Rb, 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.[39][40] For cold atom applications requiring tunable interactions, 85Rb is preferable due to its rich Feshbach spectrum.[41]

Rubidium has been used for polarizing 3He, producing volumes of magnetized 3He gas, with the nuclear spins aligned rather than random. Rubidium vapor is optically pumped by a laser and the polarized Rb polarizes 3He through the hyperfine interaction.[42] Such spin-polarized 3He cells are useful for neutron polarization measurements and for producing polarized neutron beams for other purposes.[43]

The resonant element in atomic clocks utilizes the hyperfine structure of rubidium's energy levels, and rubidium is useful for high-precision timing. It is used as the main component of secondary frequency references (rubidium oscillators) in cell site transmitters and other electronic transmitting, networking, and test equipment. These rubidium standards are often used with GPS to produce a "primary frequency standard" that has greater accuracy and is less expensive than caesium standards.[44][45] Such rubidium standards are often mass-produced for the telecommunication industry.[46]

Other potential or current uses of rubidium include a working fluid in vapor turbines, as a getter in vacuum tubes, and as a photocell component.[47] Rubidium is also used as an ingredient in special types of glass, in the production of superoxide by burning in oxygen, in the study of potassium ion channels in biology, and as the vapor in atomic magnetometers.[48] In particular, 87Rb is used with other alkali metals in the development of spin-exchange relaxation-free (SERF) magnetometers.[48]

Rubidium-82 is used for positron emission tomography. Rubidium is very similar to potassium and tissue with high potassium content will also accumulate the radioactive rubidium. One of the main uses is myocardial perfusion imaging. As a result of changes in the blood–brain barrier in brain tumors, rubidium collects more in brain tumors than normal brain tissue, allowing the use of radioisotope rubidium-82 in nuclear medicine to locate and image brain tumors.[49] Rubidium-82 has a very short half-life of 76 seconds, and the production from decay of strontium-82 must be done close to the patient.[50]

Rubidium was tested for the influence on manic depression and depression.[51][52] Dialysis patients suffering from depression show a depletion in rubidium and therefore a supplementation may help during depression.[53] In some tests the rubidium was administered as rubidium chloride with up to 720 mg per day for 60 days.[54][55]

Precautions and biological effects

GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H260, H314
P223, P231+232, P280, P305+351+338, P370+378, P422[56]
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propaneHealth code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gasReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond

Rubidium reacts violently with water and can cause fires. To ensure safety and purity, this metal is usually kept under a dry mineral oil or sealed in glass ampoules in an inert atmosphere. Rubidium forms peroxides on exposure even to small amount of air diffused into the oil, and storage is subject to similar precautions as the storage of metallic potassium.[57]

Rubidium, like sodium and potassium, almost always has +1 oxidation state when dissolved in water, even in biological contexts. The human body tends to treat Rb+ ions as if they were potassium ions, and therefore concentrates rubidium in the body's intracellular fluid (i.e., inside cells).[58] The ions are not particularly toxic; a 70 kg person contains on average 0.36 g of rubidium, and an increase in this value by 50 to 100 times did not show negative effects in test persons.[59] The biological half-life of rubidium in humans measures 31–46 days.[51] Although a partial substitution of potassium by rubidium is possible, when more than 50% of the potassium in the muscle tissue of rats was replaced with rubidium, the rats died.[60][61]

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Further reading

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

External links

Alkali metal

The alkali metals are a group (column) in the periodic table consisting of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). This group lies in the s-block of the periodic table of elements as all alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour.

The alkali metals are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen (and in the case of lithium, nitrogen). Because of their high reactivity, they must be stored under oil to prevent reaction with air, and are found naturally only in salts and never as the free elements. Caesium, the fifth alkali metal, is the most reactive of all the metals. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen (H), which is nominally a group 1 element but not normally considered to be an alkali metal as it rarely exhibits behaviour comparable to that of the alkali metals. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.

All of the discovered alkali metals occur in nature as their compounds: in order of abundance, sodium is the most abundant, followed by potassium, lithium, rubidium, caesium, and finally francium, which is very rare due to its extremely high radioactivity; francium occurs only in the minutest traces in nature as an intermediate step in some obscure side branches of the natural decay chains. Experiments have been conducted to attempt the synthesis of ununennium (Uue), which is likely to be the next member of the group, but they have all met with failure. However, ununennium may not be an alkali metal due to relativistic effects, which are predicted to have a large influence on the chemical properties of superheavy elements; even if it does turn out to be an alkali metal, it is predicted to have some differences in physical and chemical properties from its lighter homologues.

Most alkali metals have many different applications. One of the best-known applications of the pure elements is the use of rubidium and caesium in atomic clocks, of which caesium atomic clocks are the most accurate and precise representation of time. A common application of the compounds of sodium is the sodium-vapour lamp, which emits light very efficiently. Table salt, or sodium chloride, has been used since antiquity. Lithium finds use as a psychiatric medication and as an anode in lithium batteries. Sodium and potassium are also essential elements, having major biological roles as electrolytes, and although the other alkali metals are not essential, they also have various effects on the body, both beneficial and harmful.


Germane is the chemical compound with the formula GeH4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is tetrahedral. It burns in air to produce GeO2 and water. Germane is a group 14 hydride.

Igneous petrology

Igneous petrology is the study of igneous rocks—those that are formed from magma. As a branch of geology, igneous petrology is closely related to volcanology, tectonophysics, and petrology in general. The modern study of igneous rocks utilizes a number of techniques, some of them developed in the fields of chemistry, physics, or other earth sciences. Petrography, crystallography, and isotopic studies are common methods used in igneous petrology.

Isotopes of rubidium

Rubidium (37Rb) has 32 isotopes, with naturally occurring rubidium being composed of just two isotopes; 85Rb (72.2%) and the radioactive 87Rb (27.8%). Normal mixes of rubidium are radioactive enough to fog photographic film in approximately 30 to 60 days.

87Rb has a half-life of 4.92×1010 years. It readily substitutes for potassium in minerals, and is therefore fairly widespread. 87Rb has been used extensively in dating rocks; 87Rb decays to stable strontium-87 by emission of a negative beta particle, i.e. an electron ejected from the nucleus. 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 87Sr/86Sr 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.

Other than 87Rb, the longest-lived radioisotopes are 83Rb with a half-life of 86.2 days, 84Rb with a half-life of 33.1 days and 86Rb with a half-life of 18.642 days. All other radioisotopes have half-lives less than a day.

82Rb is used in some cardiac positron emission tomography scans to assess myocardial perfusion. It has a half-life of 1.273 minutes. It does not exist naturally, but can be made from the decay of 82Sr.


Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with formula K(Li,Al,Rb)2(Al,Si)4O10(F,OH)2. It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is a phyllosilicate mineral and a member of the polylithionite-trilithionite series.It is associated with other lithium-bearing minerals like spodumene in pegmatite bodies. It is one of the major sources of the rare alkali metals rubidium and caesium. In 1861, Robert Bunsen and Gustav Kirchhoff extracted 150 kg (330 lb) of lepidolite and yielded a few grams of rubidium salts for analysis, and therefore discovered the new element rubidium.It occurs in granite pegmatites, in some high-temperature quartz veins, greisens and granites. Associated minerals include quartz, feldspar, spodumene, amblygonite, tourmaline, columbite, cassiterite, topaz and beryl.Notable occurrences include Brazil; Ural Mountains, Russia; California, United States; Tanco Mine, Bernic Lake, Manitoba, Canada; and Madagascar.


Rubidium-82 (82Rb) is a radioactive isotope of rubidium. 82Rb is widely used in myocardial perfusion imaging. This isotope undergoes rapid uptake by myocardiocytes, which makes it a valuable tool for identifying myocardial ischemia in Positron Emission Tomography (PET) imaging. 82Rb is used in the pharmaceutical industry and is marketed under the trade names RUBY-FILL Rubidium Rb82 Generator and CardioGen-82.

Rubidium-82 chloride

Rubidium-82 chloride is a form of rubidium chloride containing a radioactive isotope of rubidium. It is marketed under the brand name Cardiogen-82 by Bracco Diagnostics for use in Myocardial perfusion imaging. It is rapidly taken up by heart muscle cells, and therefore can be used to identify regions of heart muscle that are receiving poor blood flow in a technique called PET perfusion imaging. The half-life of the rubidium-82 is only 1.27 minutes; it is normally produced at the place of use by rubidium generators.

Rubidium bromide

Rubidium bromide is the bromide of rubidium. It has a NaCl crystal structure, with a lattice constant of 685 picometres.There are several methods for synthesising rubidium bromide. One involves reacting rubidium hydroxide with hydrobromic acid:

RbOH + HBr → RbBr + H2OAnother method is to neutralize rubidium carbonate with hydrobromic acid:

Rb2CO3 + 2HBr → 2RbBr + H2O + CO2Rubidium metal would react directly with bromine to form RbBr, but this is not a sensible production method, since rubidium metal is substantially more expensive than the carbonate or hydroxide; moreover, the reaction would be explosive.

Rubidium chloride

Rubidium chloride is the chemical compound with the formula RbCl. This alkali metal halide is composed of rubidium and chlorine, and finds diverse uses ranging from electrochemistry to molecular biology.

Rubidium fluoride

Rubidium fluoride (RbF) is the fluoride salt of rubidium. It is a cubic crystal with rock-salt structure.

There are several methods for synthesising rubidium fluoride. One involves reacting rubidium hydroxide with hydrofluoric acid:

RbOH + HF → RbF + H2OAnother method is to neutralize rubidium carbonate with hydrofluoric acid:

Rb2CO3 + 2HF → 2RbF + H2O + CO2Another possible method is to react rubidium hydroxide with ammonium fluoride:

RbOH + NH4F → RbF + H2O + NH3The least used method due to expense of rubidium metal is to react it directly with fluorine gas, as rubidium reacts violently with halogens:

2Rb + F2 → 2RbF

Rubidium hydride

Rubidium hydride is the hydride of rubidium. It has the formula RbH and is an alkali metal hydride. It is synthesized using rubidium metal to react with hydrogen gas. As a hydride of an alkali metal, it is reactive towards even weak oxidizing agents. A redox reaction will occur with chlorine or fluorine and a lot of heat will evolve. Rubidium hydride will react violently with water or air and careful storage is necessary.

Rubidium hydrogen sulfate

Rubidium hydrogen sulfate is the rubidium salt of sulfuric acid. It has the formula RbHSO4.

Rubidium hydroxide

Rubidium hydroxide (+1) (RbOH) is a strong basic chemical and alkali that is formed by one rubidium ion and one hydroxide ion.

Rubidium hydroxide does not appear in nature. However it can be obtained by synthesis from rubidium oxide. In addition, rubidium hydroxide is commercially available in form of an aqueous solution from a few suppliers.

Rubidium hydroxide is highly corrosive, therefore suitable protective clothing, gloves and eye-face protection are required when handling this material.

Rubidium iodide

Rubidium iodide is a salt with a melting point of 642 °C. Its chemical formula is RbI.

Rubidium iodide can be formed from the reaction of rubidium and iodine:

2 Rb + I2 → 2 RbI

Rubidium nitrate

Rubidium nitrate is an inorganic compound with the formula RbNO3. This alkali metal nitrate salt is white and highly soluble in water.

Rubidium oxide

Rubidium oxide is the chemical compound with the formula Rb2O. Rubidium oxide is highly reactive towards water, and therefore it would not be expected to occur naturally. The rubidium content in minerals is often calculated and quoted in terms of Rb2O. In reality, the rubidium is typically present as a component of (actually, an impurity in) silicate or aluminosilicate. A major source of rubidium is lepidolite, KLi2Al(Al,Si)3O10(F,OH)2, wherein Rb sometimes replaces K.

Rb2O is a yellow colored solid. The related species Na2O, K2O, and Cs2O are colorless, pale-yellow, and orange, respectively.

The alkali metal oxides M2O (M = Li, Na, K, Rb) crystallise in the antifluorite structure. In the antifluorite motif the positions of the anions and cations are reversed relative to their positions in CaF2, with rubidium ions 8 coordinate (cubic) and oxide ions 4 coordinate (tetrahedral).

Rubidium sulfate

Rubidium sulfate is a sulfate of rubidium. The molecular formula of the compound is Rb2SO4. The molecular weight of this compound is 266.999 g/mol. An acid sulfate exists, rubidium hydrogen sulfate.

Rubidium telluride

Rubidium telluride is the inorganic compound with the formula Rb2Te. It is a yellow-green powder that melts at either 775 °C or 880 °C (two different values have been reported). It is an obscure material of minor academic interest.Like other alkali metal chalcogenides, Rb2Te is prepared from the elements in liquid ammonia.Rubidium telluride is used in some space-based UV detectors.

Rubidium compounds

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