Difference between revisions of "Cesium" - New World Encyclopedia
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| − | {{Elementbox_header | number=55 | symbol=Cs | name= | + | {{Elementbox_header | number=55 | symbol=Cs | name=cesium | left=[[xenon]] | right=[[barium]] | above=[[rubidium|Rb]] | below=[[francium|Fr]] | color1=#ff6666 | color2=black }} |
{{Elementbox_series | [[alkali metal]]s }} | {{Elementbox_series | [[alkali metal]]s }} | ||
{{Elementbox_groupperiodblock | group=1 | period=6 | block=s }} | {{Elementbox_groupperiodblock | group=1 | period=6 | block=s }} | ||
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{{Elementbox_brinellhardness_mpa | 0.14 }} | {{Elementbox_brinellhardness_mpa | 0.14 }} | ||
{{Elementbox_cas_number | 7440-46-2 }} | {{Elementbox_cas_number | 7440-46-2 }} | ||
| − | {{Elementbox_isotopes_begin | isotopesof= | + | {{Elementbox_isotopes_begin | isotopesof=cesium | color1=#ff6666 | color2=black }} |
{{Elementbox_isotopes_stable | mn=133 | sym=Cs | na=100% | n=78 }} | {{Elementbox_isotopes_stable | mn=133 | sym=Cs | na=100% | n=78 }} | ||
{{Elementbox_isotopes_decay2 | mn=134 | sym=Cs | {{Elementbox_isotopes_decay2 | mn=134 | sym=Cs | ||
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* It is most notably used in [[atomic clock]]s. | * It is most notably used in [[atomic clock]]s. | ||
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==Discovery== | ==Discovery== | ||
Cesium (from the [[Latin]] word ''caesius'', meaning "sky blue" or "heavenly blue") was discovered by [[Robert Bunsen]]* and [[Gustav Kirchhoff]]* in 1860, when they analyzed the spectrum of [[mineral water]]* obtained from Dürkheim, Germany. They held a drop of the water in a flame and observed the spectral lines of several elements. Among these lines they observed two blue lines that did not come from any of the known elements. They concluded that the blue lines were produced by a hitherto unknown element, which they named cesium. Thus cesium became the first element discovered by spectral analysis. Bunsen isolated cesium salts from the spring water, but the metal itself was isolated in 1881 by Carl Setterberg, who worked in Bunsen's laboratory. | Cesium (from the [[Latin]] word ''caesius'', meaning "sky blue" or "heavenly blue") was discovered by [[Robert Bunsen]]* and [[Gustav Kirchhoff]]* in 1860, when they analyzed the spectrum of [[mineral water]]* obtained from Dürkheim, Germany. They held a drop of the water in a flame and observed the spectral lines of several elements. Among these lines they observed two blue lines that did not come from any of the known elements. They concluded that the blue lines were produced by a hitherto unknown element, which they named cesium. Thus cesium became the first element discovered by spectral analysis. Bunsen isolated cesium salts from the spring water, but the metal itself was isolated in 1881 by Carl Setterberg, who worked in Bunsen's laboratory. | ||
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==Occurrence== | ==Occurrence== | ||
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Cesium is the least abundant of the five nonradioactive alkali metals. Technically, [[francium]] is the least common alkali metal, but because it is highly radioactive and its total worldwide quantity is estimated to be only 340 to 550 grams, its abundance can be considered zero in practical terms.<ref>{{cite journal| url=http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm| journal=The Chemical Educator| volume=10| issue=5| month=09/23| year=2005| {{doi|10.1333/s00897050956a}}| title=Francium (Atomic Number 87), the Last Discovered Natural Element| first=Jean-Pierre| last=Adloff| coauthors=George B. Kauffman| accessdate=2006-05-16}}</ref> | Cesium is the least abundant of the five nonradioactive alkali metals. Technically, [[francium]] is the least common alkali metal, but because it is highly radioactive and its total worldwide quantity is estimated to be only 340 to 550 grams, its abundance can be considered zero in practical terms.<ref>{{cite journal| url=http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm| journal=The Chemical Educator| volume=10| issue=5| month=09/23| year=2005| {{doi|10.1333/s00897050956a}}| title=Francium (Atomic Number 87), the Last Discovered Natural Element| first=Jean-Pierre| last=Adloff| coauthors=George B. Kauffman| accessdate=2006-05-16}}</ref> | ||
| − | Along with [[gallium]], francium, and [[mercury (element)|mercury]], cesium is among the few metals that are liquid at or near room [[temperature]]. Its melting point is 28.44°C. | + | Along with [[gallium]], francium, and [[mercury (element)|mercury]], cesium is among the few metals that are liquid at or near room [[temperature]]. Its melting point is 28.44°C. |
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| + | Cesium reacts explosively when it comes in contact with [[water]] (even cold water), and also reacts with ice at temperatures above −116°C. The reaction with water produces cesium [[hydroxide]]* (CsOH), an extremely strong chemical [[base (chemistry)|base]]* that will rapidly etch the surface of [[glass]]. In addition cesium reacts violently with chlorine gas to produce cesium chloride (CsCl). | ||
===Isotopes=== | ===Isotopes=== | ||
| − | Cesium has at least 39 known [[isotope]]s which is more than any other element, except for [[francium]]. The [[atomic mass]]*es of these isotopes range from 112 to 151. Yet it has only one naturally occurring stable isotope: <sup>133</sup>Cs. | + | Cesium has at least 39 known [[isotope]]s which is more than any other element, except for [[francium]]. The [[atomic mass]]*es of these isotopes range from 112 to 151. Yet it has only one naturally occurring stable isotope: <sup>133</sup>Cs. Most of the other isotopes (except for those noted in the table) have [[half-life|half-lives]]* from a few days to fractions of a second. |
| − | The isotope <sup>137</sup>Cs has been used in hydrologic studies, analogous to the use of tritium (<sup>3</sup>H). | + | The isotope <sup>137</sup>Cs, with a half-life of 30.17 years, has been used in hydrologic studies, analogous to the use of tritium (<sup>3</sup>H). It decomposes to barium-137 (a short-lived product of decay), then to a form of nonradioactive barium. |
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| − | Cesium-137 | + | Cesium-137 is produced during the detonation of [[nuclear weapon]]s and in [[nuclear power plant]]*s. It was a notable product during the 1986 [[Chernobyl]]* meltdown. Beginning in 1945, with the commencement of [[nuclear testing]]*, <sup>137</sup>Cs has been released into the [[Earth's atmosphere|atmosphere]], where it is absorbed by moisture and returned to the Earth's surface as a component of [[radioactive fallout]]*. Once <sup>137</sup>Cs enters groundwater, it is deposited on soil surfaces and removed from the landscape primarily by [[particle transport]]*. |
==Applications== | ==Applications== | ||
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| − | *<sup>134</sup>Cs has been used in [[hydrology]] as a measure of | + | * Cesium is most notably used in [[atomic clock]]*s, which are accurate to seconds in many thousands of years. Since 1967, the [[SI|International System of Measurements]] bases its unit of [[time]], the [[second]]*, on the properties of cesium. |
| − | *Like other group 1 elements, | + | *<sup>134</sup>Cs has been used in [[hydrology]] as a measure of cesium output by the [[nuclear power]]* industry. This isotope is used because, while it is less prevalent than either <sup>133</sup>Cs or <sup>137</sup>Cs, <sup>134</sup>Cs can be produced solely by nuclear reactions. <sup>135</sup>Cs has also been used for this purpose. |
| − | *This metal is also used in [[photoelectric cell]]s | + | *Like other group 1 elements, cesium has great affinity for [[oxygen]] and is used as a "[[getter]]*" in [[vacuum tube]]*s. |
| − | * | + | *This metal is also used in [[photoelectric cell]]*s because it readily emits [[electron]]s. |
| − | *[[Radioactive decay|Radioactive]] isotopes of | + | *Cesium is used as a [[catalyst]]* in the [[hydrogenation]]* of certain [[organic compound]]s. |
| − | *[[ | + | *[[Radioactive decay|Radioactive]] isotopes of cesium are used in medicine to treat certain types of [[cancer]]. |
| − | * | + | *[[Cesium fluoride]]* is widely used in [[organic chemistry]] as a [[Base (chemistry)|base]]* and as a source of [[anhydrous]]* [[fluoride]]* ion. |
| − | *Because of their high density, [[ | + | *Cesium vapor is used in many common [[magnetometers]]*. |
| − | * | + | *Because of their high density, [[cesium chloride]]* solutions are commonly used in molecular biology experiments for the isolation of nucleic acids by a technique known as "density gradient ultracentrifugation." |
| + | *Recently, this metal has been used in [[ion propulsion]]* systems. | ||
*Cesium-137 is an extremely common isotope in industrial applications such as: | *Cesium-137 is an extremely common isotope in industrial applications such as: | ||
**moisture density gauges | **moisture density gauges | ||
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**well-logging devices (used to measure the thickness of rock-strata) | **well-logging devices (used to measure the thickness of rock-strata) | ||
| + | ==Precautions== | ||
| + | All alkali metals are highly reactive. As one of the heavier alkali [[metal]]s, cesium is also one of the most reactive. As noted above, it is highly [[explosive]] when it comes in contact with [[water]] or ice. [[Cesium hydroxide]]* is an extremely strong base and can attack [[glass]]. | ||
| + | All cesium compounds should be regarded as mildly toxic, because of its chemical similarity to [[potassium]]. Contact with large amounts can cause [[hyperirritability]]* and [[spasms]]*. On the other hand, such amounts would not ordinarily be encountered in nature, so cesium is not a major chemical environmental pollutant. Rats fed with cesium in place of potassium in their diet were found to die, so this element cannot replace potassium in function. | ||
| + | The [[isotope]]*s <sup>134</sup>Cs and <sup>137</sup>Cs (present in the [[biosphere]] in small amounts as a result of radiation leaks) represent a radioactivity burden that varies depending on location. Radioactive cesium does not accumulate in the body as effectively as many other fission products, such as radioactive iodine or strontium. | ||
| + | ==See also== | ||
| + | *[[Periodic table]] | ||
| + | *[[Chemical element]] | ||
| − | == | + | == Footnote == |
| − | + | <div class="references-small"><references/> | |
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| − | == | + | ==Reference== |
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*[http://periodic.lanl.gov/elements/55.html Los Alamos National Laboratory - Cesium]</div> | *[http://periodic.lanl.gov/elements/55.html Los Alamos National Laboratory - Cesium]</div> | ||
Revision as of 23:48, 25 August 2006
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| General | ||||||||||||||||||||||||||||||||||
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| Name, Symbol, Number | cesium, Cs, 55 | |||||||||||||||||||||||||||||||||
| Chemical series | alkali metals | |||||||||||||||||||||||||||||||||
| Group, Period, Block | 1, 6, s | |||||||||||||||||||||||||||||||||
| Appearance | silvery gold 
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| Atomic mass | 132.9054519(2) g/mol | |||||||||||||||||||||||||||||||||
| Electron configuration | [Xe] 6s1 | |||||||||||||||||||||||||||||||||
| Electrons per shell | 2, 8, 18, 18, 8, 1 | |||||||||||||||||||||||||||||||||
| Physical properties | ||||||||||||||||||||||||||||||||||
| Phase | solid | |||||||||||||||||||||||||||||||||
| Density (near r.t.) | 1.93 g/cm³ | |||||||||||||||||||||||||||||||||
| Liquid density at m.p. | 1.843 g/cm³ | |||||||||||||||||||||||||||||||||
| Melting point | 301.59 K (28.44 °C, 83.19 °F) | |||||||||||||||||||||||||||||||||
| Boiling point | 944 K (671 °C, 1240 °F) | |||||||||||||||||||||||||||||||||
| Critical point | 1938 K, 9.4 MPa | |||||||||||||||||||||||||||||||||
| Heat of fusion | 2.09 kJ/mol | |||||||||||||||||||||||||||||||||
| Heat of vaporization | 63.9 kJ/mol | |||||||||||||||||||||||||||||||||
| Heat capacity | (25 °C) 32.210 J/(mol·K) | |||||||||||||||||||||||||||||||||
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| Atomic properties | ||||||||||||||||||||||||||||||||||
| Crystal structure | cubic body centered | |||||||||||||||||||||||||||||||||
| Oxidation states | 1 (strongly basic oxide) | |||||||||||||||||||||||||||||||||
| Electronegativity | 0.79 (Pauling scale) | |||||||||||||||||||||||||||||||||
| Ionization energies | 1st: 375.7 kJ/mol | |||||||||||||||||||||||||||||||||
| 2nd: 2234.3 kJ/mol | ||||||||||||||||||||||||||||||||||
| 3rd: 3400 kJ/mol | ||||||||||||||||||||||||||||||||||
| Atomic radius | 260 pm | |||||||||||||||||||||||||||||||||
| Atomic radius (calc.) | 298 pm | |||||||||||||||||||||||||||||||||
| Covalent radius | 225 pm | |||||||||||||||||||||||||||||||||
| Miscellaneous | ||||||||||||||||||||||||||||||||||
| Magnetic ordering | no data | |||||||||||||||||||||||||||||||||
| Electrical resistivity | (20 °C) 205 nΩ·m | |||||||||||||||||||||||||||||||||
| Thermal conductivity | (300 K) 35.9 W/(m·K) | |||||||||||||||||||||||||||||||||
| Thermal expansion | (25 °C) 97 µm/(m·K) | |||||||||||||||||||||||||||||||||
| Speed of sound (thin rod) | (r.t.) 1.7 m/s | |||||||||||||||||||||||||||||||||
| Bulk modulus | 1.6 GPa | |||||||||||||||||||||||||||||||||
| Mohs hardness | 0.2 | |||||||||||||||||||||||||||||||||
| Brinell hardness | 0.14 MPa | |||||||||||||||||||||||||||||||||
| CAS registry number | 7440-46-2 | |||||||||||||||||||||||||||||||||
| Notable isotopes | ||||||||||||||||||||||||||||||||||
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Cesium (also spelled caesium, chemical symbol Cs, atomic number 55) is a member of the group of chemical elements known as alkali metals. Soft and silvery gold in color, it readily liquefies at warm temperatures.
- It is most notably used in atomic clocks.
Discovery
Cesium (from the Latin word caesius, meaning "sky blue" or "heavenly blue") was discovered by Robert Bunsen and Gustav Kirchhoff in 1860, when they analyzed the spectrum of mineral water obtained from Dürkheim, Germany. They held a drop of the water in a flame and observed the spectral lines of several elements. Among these lines they observed two blue lines that did not come from any of the known elements. They concluded that the blue lines were produced by a hitherto unknown element, which they named cesium. Thus cesium became the first element discovered by spectral analysis. Bunsen isolated cesium salts from the spring water, but the metal itself was isolated in 1881 by Carl Setterberg, who worked in Bunsen's laboratory.
Occurrence
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Cesium occurs in several minerals, particularly lepidolite and pollucite (a hydrated silicate of aluminum and cesium). One of the world's most significant and rich sources of this metal is located at Bernic Lake in Manitoba. The deposits there are estimated to contain 300,000 metric tons of pollucite, at an average of 20% cesium.
It can be isolated by electrolysis of fused cyanide and in several other ways. Exceptionally pure, gas-free cesium can be made by decomposing cesium azide with heat. The primary compounds of cesium are its chloride and its nitrate.
Notable characteristics
As an alkali metal, cesium is part of group 1 of the periodic table, between rubidium and francium. Also, it lies in period 6, just before barium. This silvery gold metal is soft and ductile (it can be readily drawn into wires).
As noted above, the spectrum of cesium has two bright lines in the blue part of the electromagnetic spectrum. In addition, its spectrum has several other lines in the red, yellow, and green regions.
Cesium is the most electropositive and most alkaline of the stable chemical elements. Aside from francium, it has the lowest ionization potential of all the elements, which means that it readily loses its outermost electron to become an ion. (Ionization potential is the energy needed to remove an electron from the atom's outermost shell.)
Cesium is the least abundant of the five nonradioactive alkali metals. Technically, francium is the least common alkali metal, but because it is highly radioactive and its total worldwide quantity is estimated to be only 340 to 550 grams, its abundance can be considered zero in practical terms.[1]
Along with gallium, francium, and mercury, cesium is among the few metals that are liquid at or near room temperature. Its melting point is 28.44°C.
Cesium reacts explosively when it comes in contact with water (even cold water), and also reacts with ice at temperatures above −116°C. The reaction with water produces cesium hydroxide (CsOH), an extremely strong chemical base that will rapidly etch the surface of glass. In addition cesium reacts violently with chlorine gas to produce cesium chloride (CsCl).
Isotopes
Cesium has at least 39 known isotopes which is more than any other element, except for francium. The atomic masses of these isotopes range from 112 to 151. Yet it has only one naturally occurring stable isotope: 133Cs. Most of the other isotopes (except for those noted in the table) have half-lives from a few days to fractions of a second.
The isotope 137Cs, with a half-life of 30.17 years, has been used in hydrologic studies, analogous to the use of tritium (3H). It decomposes to barium-137 (a short-lived product of decay), then to a form of nonradioactive barium.
Cesium-137 is produced during the detonation of nuclear weapons and in nuclear power plants. It was a notable product during the 1986 Chernobyl meltdown. Beginning in 1945, with the commencement of nuclear testing, 137Cs has been released into the atmosphere, where it is absorbed by moisture and returned to the Earth's surface as a component of radioactive fallout. Once 137Cs enters groundwater, it is deposited on soil surfaces and removed from the landscape primarily by particle transport.
Applications
- Cesium is most notably used in atomic clocks, which are accurate to seconds in many thousands of years. Since 1967, the International System of Measurements bases its unit of time, the second, on the properties of cesium.
- 134Cs has been used in hydrology as a measure of cesium output by the nuclear power industry. This isotope is used because, while it is less prevalent than either 133Cs or 137Cs, 134Cs can be produced solely by nuclear reactions. 135Cs has also been used for this purpose.
- Like other group 1 elements, cesium has great affinity for oxygen and is used as a "getter" in vacuum tubes.
- This metal is also used in photoelectric cells because it readily emits electrons.
- Cesium is used as a catalyst in the hydrogenation of certain organic compounds.
- Radioactive isotopes of cesium are used in medicine to treat certain types of cancer.
- Cesium fluoride is widely used in organic chemistry as a base and as a source of anhydrous fluoride ion.
- Cesium vapor is used in many common magnetometers.
- Because of their high density, cesium chloride solutions are commonly used in molecular biology experiments for the isolation of nucleic acids by a technique known as "density gradient ultracentrifugation."
- Recently, this metal has been used in ion propulsion systems.
- Cesium-137 is an extremely common isotope in industrial applications such as:
- moisture density gauges
- leveling gauges
- thickness gauges
- well-logging devices (used to measure the thickness of rock-strata)
Precautions
All alkali metals are highly reactive. As one of the heavier alkali metals, cesium is also one of the most reactive. As noted above, it is highly explosive when it comes in contact with water or ice. Cesium hydroxide is an extremely strong base and can attack glass.
All cesium compounds should be regarded as mildly toxic, because of its chemical similarity to potassium. Contact with large amounts can cause hyperirritability and spasms. On the other hand, such amounts would not ordinarily be encountered in nature, so cesium is not a major chemical environmental pollutant. Rats fed with cesium in place of potassium in their diet were found to die, so this element cannot replace potassium in function.
The isotopes 134Cs and 137Cs (present in the biosphere in small amounts as a result of radiation leaks) represent a radioactivity burden that varies depending on location. Radioactive cesium does not accumulate in the body as effectively as many other fission products, such as radioactive iodine or strontium.
See also
Footnote
- ↑ Adloff, Jean-Pierre and George B. Kauffman (09/23 2005). Francium (Atomic Number 87), the Last Discovered Natural Element. The Chemical Educator 10 (5).
Reference
External links
- Origins of the Element Names
- Video of alkali metals reacting with water
- WebElements.com – Caesium
- FAQ from alt.cesium newsgroup
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