Rubidium
25599
226178394
2008-07-17T04:50:23Z
Arkuat
29003
/* Characteristics */ section title per discussion at [[WP:WikiProject Elements]]
{{Elementbox_header | number=37 | symbol=Rb | name=rubidium | left=[[krypton]] | right=[[strontium]] | above=[[potassium|K]] | below=[[caesium|Cs]] | color1=#ff6666 | color2=black }}
{{Elementbox_series | [[alkali metal]]s }}
{{Elementbox_groupperiodblock | group=1 | period=5 | block=s }}
{{Elementbox_appearance_img |Rb66| grey white }}
{{Elementbox_atomicmass_gpm | [[1 E-25 kg|85.4678]][[List of elements by atomic mass|(3)]] }}
{{Elementbox_econfig | [[[krypton|Kr]]] 5s<sup>1</sup> }}
{{Elementbox_epershell | 2, 8, 18, 8, 1 }}
{{Elementbox_section_physicalprop | color1=#ff6666 | color2=black }}
{{Elementbox_phase | [[solid]] }}
{{Elementbox_density_gpcm3nrt | 1.532 }}
{{Elementbox_densityliq_gpcm3mp | 1.46 }}
{{Elementbox_meltingpoint | k=312.46 | c=39.31 | f=102.76 }}
{{Elementbox_boilingpoint | k=961 | c=688 | f=1270 }}
{{Elementbox_criticalpoint | k=(extrapolated)<br />2093 | mpa=16 }}
{{Elementbox_heatfusion_kjpmol | 2.19 }}
{{Elementbox_heatvaporiz_kjpmol | 75.77 }}
{{Elementbox_heatcapacity_jpmolkat25 | 31.060 }}
{{Elementbox_vaporpressure_katpa | 434 | 486 | 552 | 641 | 769 | 958 | comment= }}
{{Elementbox_section_atomicprop | color1=#ff6666 | color2=black }}
{{Elementbox_crystalstruct | cubic body centered }}
{{Elementbox_oxistates | 1<br />(strongly [[base (chemistry)|basic]] oxide) }}
{{Elementbox_electroneg_pauling | 0.82 }}
{{Elementbox_ionizationenergies4 | 403.0 | 2633 | 3860 }}
{{Elementbox_atomicradius_pm | [[1 E-10 m|235]] }}
{{Elementbox_atomicradiuscalc_pm | [[1 E-10 m|265]] }}
{{Elementbox_covalentradius_pm | [[1 E-10 m|211]] }}
{{Elementbox_vanderwaalsrad_pm | [[1 E-10 m|244]] }}
{{Elementbox_section_miscellaneous | color1=#ff6666 | color2=black }}
{{Elementbox_magnetic | no data }}
{{Elementbox_eresist_ohmmat20 | 128 n}}
{{Elementbox_thermalcond_wpmkat300k | 58.2 }}
{{Elementbox_speedofsound_rodmpsat20 | 1300 }}
{{Elementbox_youngsmodulus_gpa | 2.4 }}
{{Elementbox_bulkmodulus_gpa | 2.5 }}
{{Elementbox_mohshardness | 0.3 }}
{{Elementbox_brinellhardness_mpa | 0.216 }}
{{Elementbox_cas_number | 7440-17-7 }}
{{Elementbox_isotopes_begin | color1=#ff6666 | color2=black }}
{{Elementbox_isotopes_decay2 | mn=83 | sym=Rb
| na=[[synthetic radioisotope|syn]] | hl=86.2 [[day|d]]
| dm1=[[electron capture|ε]] | de1=- | pn1=83 | ps1=[[krypton|Kr]]
| dm2=[[gamma radiation|γ]] | de2=0.52, 0.53,<br />0.55 | pn2= | ps2=- }}
{{Elementbox_isotopes_decay4 | mn=84 | sym=Rb
| na=[[synthetic radioisotope|syn]] | hl=32.9 d
| dm1=ε | de1=- | pn1=84 | ps1=[[krypton|Kr]]
| dm2=[[positron emission|β<sup>+</sup>]] | de2=1.66, 0.78 | pn2=84 | ps2=[[krypton|Kr]]
| dm3=γ | de3=0.881 | pn3= | ps3=-
| dm4=[[beta decay|β<sup>-</sup>]] | de4=0.892 | pn4=84 | ps4=[[strontium|Sr]] }}
{{Elementbox_isotopes_stable | mn=85 | sym=Rb | na=72.168% | n=48 }}
{{Elementbox_isotopes_decay2 | mn=86 | sym=Rb
| na=[[synthetic radioisotope|syn]] | hl=18.65 d
| dm1=β<sup>-</sup> | de1=1.775 | pn1=86 | ps1=[[strontium|Sr]]
| dm2=γ | de2=1.0767 | pn2= | ps2=- }}
{{Elementbox_isotopes_decay | mn=87 | sym=Rb
| na=27.835% | hl=4.88{{e|10}} [[year|y]]
| dm=β<sup>-</sup> | de=0.283 | pn=87 | ps=[[strontium|Sr]] }}
{{Elementbox_isotopes_end}}
{{Elementbox_footer | color1=#ff6666 | color2=black }}
'''Rubidium''' ({{pronEng|ruːˈbɪdiəm}}, {{IPA|/rəˈbɪdiəm/}}) 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. Rb-87, a naturally occurring [[isotope]], is very slightly [[radioactive]], with a half-life of 4.88{{e|10}} years, which, at 49 billion years, is longer than the estimated [[Age_of_the_universe|age of the universe]]. Rubidium is very soft and highly reactive, with properties similar to other elements in group 1, like rapid [[oxidation]] in [[Earth's atmosphere|air]].
== Characteristics ==
Rubidium is the second most [[electropositive]] of the stable alkali elements and liquefies at high ambient temperature (102.7 °F = 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 [[amalgam]]s with [[mercury (element)|mercury]] and it can form [[alloy]]s with [[gold]], [[caesium]], [[sodium]], and [[potassium]]. The element gives a reddish-violet color to a flame, hence its name.
== Uses ==
Potential or current uses of rubidium include:
*A [[Bose-Einstein condensate]].
*A working fluid in [[vapor turbine]]s.
*A [[getter]] in [[vacuum tube]]s.
*A [[photocell]] component.
*The resonant element in [[atomic clock]]s. 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 vapor has been used to make atomic [[magnetometer]]s. <sup>87</sup>Rb is currently being used, with other alkali metals, in the development of spin-exchange relaxation-free [[SERF|(SERF) magnetometers]].<ref>{{cite journal| url=http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000089000013134105000001&idtype=cvips&gifs=yes | title=Parametric modulation of an atomic magnetometer| author=Li, Zhimin et al.| journal=Applied Physics Letters| volume=89|date=2006|pages=134105 | doi=10.1063/1.2357553}}</ref>
Rubidium is easily ionized, so it has been considered for use in [[ion engine]]s for [[space vehicle]]s (but [[caesium]] and [[xenon]] are more efficient for this purpose).
Rubidium compounds are sometimes used in [[fireworks]] to give them a purple color.
[[Rubidium silver iodide|RbAg<sub>4</sub>I<sub>5</sub>]] has the highest [[room temperature]] [[electrical conductivity|conductivity]] of any known [[ionic crystal]]. This property could be useful in thin film [[battery (electricity)|batteries]] and in other applications.
Rubidium has also been considered for use in a [[thermoelectric]] generator using the [[magnetohydrodynamics|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 (electrical engineering)|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>{{cite journal| url=http://nvl.nist.gov/pub/nistpubs/jres/110/3/j110-3gen.pdf|journal=Journal of Research of the National Institute of Standards and Technology|title=Polarized 3He spin filters for slow neutron physics|author=Gentile, T.R. et al.|volume=100|pages=299}} </ref> [[Spin polarization|Spin-polarized]] <sup>3</sup>He cells are becoming popular for neutron polarization measurements and for producing polarized neutron beams for other purposes.<ref>{{cite web| url=http://www.ncnr.nist.gov/AnnualReport/FY2002_html/pages/neutron_spin.htm |publisher=NIST Center for Neutron Research 2002 Annual Report|title=Neutron spin filters based on polarized helium-3|access-date=2008-01-11}} </ref>
== History ==
Rubidium ([[Latin|L]] ''rubidus'', deepest red) was discovered in 1862 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. However, this element 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-88 was used to make a [[Bose-Einstein condensate]]<ref>{{cite web | title = Bose-Einstein Condensation | work = World of Physics on Bose-Einstein Condensation | publisher = BookRags | url = http://www.bookrags.com/Bose%E2%80%93Einstein_condensate | accessdate = 2008-01-26 }}</ref>, for which the discoverers won the 2001 [[Nobel Prize in Physics]]<ref>{{cite web | last = Levi | first = Barbara Goss | title = Cornell, Ketterle, and Wieman Share Nobel Prize for Bose-Einstein Condensates | work = Search & Discovery | publisher = Physics Today online | date = 2001 | url = http://www.physicstoday.org/pt/vol-54/iss-12/p14.html | accessdate = 2008-01-26 }}</ref>.
== Occurrence ==
Rubidium is about the sixteenth [[Abundance of elements in Earth's crust|most abundant metal in the Earth's crust]], roughly as abundant as zinc and rather more common than copper. It occurs naturally in the minerals [[leucite]], [[pollucite]], 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 chloride]]s also contain the element in commercially significant amounts. One notable source is also in the extensive deposits of [[pollucite]] at [[Bernic Lake]], [[Manitoba]].
Rubidium metal can be produced by [[redox|reducing]] rubidium chloride with [[calcium]] among other methods. In 1997 the cost of this metal in small quantities was about [[US dollar|US$]]25/[[gram]].
== Isotopes ==
{{main|Isotopes of rubidium}}
There are 26 [[isotope]]s 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 [[Becquerel|Bq]]/g, enough to fog [[photographic film]] in approximately 30 to 60 days.
Rb-87 has a [[half-life]] of 4.88{{e|10}} years. It readily substitutes for [[potassium]] in [[mineral]]s, and is therefore fairly widespread. Rb has been used extensively in [[rock dating|dating rocks]]; Rb-87 decays to stable [[strontium]]-87 by emission of a negative [[beta particle]]. During [[Fractional crystallization (geology)|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 [[rock differentiation|differentiation]]. Highest ratios (10 or higher) occur in [[pegmatite]]s. 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.
==Compounds==
{{more|:Category:Rubidium compounds}}
[[Rubidium 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 [[Rubidium oxide|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>0). 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.{{fact|date=December 2007}}
== 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]], in a [[vacuum]] or in an inert atmosphere.
== Biological effects ==
Rubidium, like sodium and potassium, is almost always in its +1 oxidation state. The human body tends to treat Rb<sup>+</sup> ions as if they were potassium ions, and therefore concentrates rubidium in the body's electrolytic fluid. The ions are not particularly toxic, and are relatively quickly removed in the sweat and urine. However, taken in excess it can be dangerous.
==References==
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==Sources==
*[http://periodic.lanl.gov/elements/37.html Los Alamos National Laboratory – Rubidium]
*Louis Meites, Handbook of Analytical Chemistry (New York: McGraw-Hill Book Company, 1963)
*{{cite web| author=Daniel A. Steck| title=Rubidium-87 D Line Data | url=http://george.ph.utexas.edu/~dsteck/alkalidata/rubidium87numbers.pdf| publisher=Los Alamos National Laboratory (technical report LA-UR-03-8638)}}
==External links==
{{Commons|Rubidium}}
{{wiktionary|rubidium}}
*[http://www.webelements.com/webelements/elements/text/Rb/index.html WebElements.com – Rubidium]
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[[Category:Chemical elements]]
[[Category:Alkali metals]]
[[Category:Rubidium|*]]
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