|Boiling Point: 944°K, 671°C, 1240°F
Melting Point: 301.7°K, 28.55°C, 83.39°F
Electrons Energy Level: 2, 8, 18, 18, 8, 1
Isotopes: 39 + 1 Stable
Heat of Vaporization: 67.74 kJ/mol
Heat of Fusion: 2.092 kJ/mol
Density: 1.873 g/cm3 @ 300°K
Specific Heat: 0.24 J/g°K
Atomic Radius: 3.34Å
Ionic Radius: 1.67Å
Electronegativity: 0.79 (Pauling); 0.86 (Allrod Rochow)
|Caesium (Latin, caesius
meaning "sky blue" or "light blue") was spectroscopically discovered by
German chemists Robert William
Bunsen and Gustav Robert Kirchhoffin 1860 in mineral water from Dürkheim, Germany.
Its identification was based upon the bright blue lines in
its spectrum and it was the first element discovered by spectrum analysis. The first
Cesium metal was produced in 1882 by Carl Setterberg. Historically, the most
important use for Cesium has been in research and development, primarily in chemical and
Also spelled Cesium, it is a soft silvery-gold alkali metal with a melting point of 28 °C (83 °F) which makes it one of the metals that are liquid at or near room temperature along with Rubidium (39°C), Francium (27 °C), Mercury (-39 °C), and Gallium (30 °C). This element is most notably used in atomic clocks.
The variant spelling cesium is sometimes used, especially in North American English, but caesium is the spelling used by the IUPAC, although since 1993 it has recognized cesium as a variant as well.
Cesium is so reactive that it will even explode on contact with ice. It has been used as a "getter" in the manufacture of vacuum tubes (i.e., it helps remove trace quantities of remaining gases). An isotope of Cesium is used in the atomic clocks.
1s2 2s2p6 3s2p6d10 4s2p6d10 5s2p6 6s1
The electromagnetic spectrum of Cesium has two bright lines in the blue part of the spectrum along with several other lines in the red, yellow, and green. This metal is silvery gold in color and is both soft and ductile. Cesium is the second most electropositive and alkaline of the chemical elements and has the second lowest ionization potential (after Francium). Cesium is the least abundant of the five non-radioactive alkali metals. (Technically, Francium is the least common alkali metal, but since it is highly radioactive with an estimated 550 grams in the entire Earth's crust at one time, its abundance can be considered zero in practical terms.)
Cesium has the second lowest melting point of all metallic elements, which limits its uses. Cesium readily combines with Oxygen and is used as a getter, a material that combines with and removes trace gases from vacuum tubes. Cesium is also used in atomic clocks, in photoelectric cells and as a catalyst in the hydrogenation of certain organic compounds. Since it is easily ionized and has a high mass, cesium ions may one day be used as a propellant in ion engines on spacecraft.
Along with Gallium, Francium, and Mercury, Cesium is among the only metals that are liquid at or near room temperature. Cesium reacts explosively in cold water and also reacts with ice at temperatures above -116°C (157°K).
Cesium Hydroxide (CsOH) is a very strong base and will rapidly etch the surface of glass. CsOH is often stated to be the "strongest base" (after FrOH), but in fact many compounds such as n-butyllithium and Sodium Amide are stronger.
There is an account that Cesium, reacting with Fluorine, takes up more Fluorine than it stoichiometrically should. It is possible that, after the salt Cs+F- has formed, the Cs+ ion, which has the same electronic structure as elemental Xenon, can like Xenon be oxidized further by Fluorine and form traces of a higher Fluoride such as CsF3, analogous to XeF2.
Today, cesium is primarily obtained from the mineral Pollucite (CsAlSi2O6). Obtaining pure Cesium is difficult since Cesium ores are frequently contaminated with Rubidium, an element that is chemically similar to Cesium. To obtain pure Cesium, Cesium and Rubidium ores are crushed and heated with Sodium metal to 650°C, forming an alloy that can then be separated with a process known as fractional distillation. Metallic Cesium is too reactive to easily handle and is usually sold in the form of Cesium Azide (CsN3). Cesium is recovered from Cesium Azide by heating it.
An alkali metal, Cesium occurs in Lepidolite, Pollucite (hydrated Silicate of Aluminum and Cesium) and within other sources. One of the world's most significant and rich sources of this metal is at Bernic Lake in Manitoba, Canada. 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 Cesium Cyanide and in a number of other ways. Exceptionally pure and gas-free Cesium can be made by the thermal decomposition of Cesium Azide. The primary compounds of Cesium are Cesium Chloride and its Nitrate. The price of Cesium metal in 1997 was about $30 per gram, but its compounds are much cheaper.
Probably the most widespread use of Cesium today is in Cesium Formate-based drilling fluids for the oil industry. The high density of the Cesium Formate brine (up to 2.3 sg,) coupled with the relative benignity of 133Cs , reduces the requirement for toxic high-density suspended solids in the drilling fluid, which is a significant technological, engineering and environmental advantage.
Cesium is also 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. SI defines the second as 9,192,631,770 cycles of the radiation which corresponds to the transition between two electron spin energy levels of the ground state of the 133Cs atom.
Cesium Chloride (CsCl) and Cesium Nitrate (CsNO3) are Cesium's most common compounds and are primarily used in the production of other chemicals.
|Cesium Hydroxide, CsOH||Cesium Cyanide, CsCN|
|Cesium Azide, CsN3||Cesium Fluoride, CsFl|
|Cesium Chloride, CsCl||Cesium Nitrate, CsNO3|
Cesium has at least 39 known isotopes, which is more than any other element except Francium. The atomic masses of these isotopes range from 112 to 151. Even though this element has a large number of isotopes, it has only one naturally occurring stable isotope, 133Cs. Most of the other isotopes have half-lives from a few days to fractions of a second. The radiogenic isotope 137Cs has been used in hydrologic studies, analogous to the use of 3H. 137Cs is produced from the detonation of nuclear weapons and is produced in nuclear power plants, and was released to the atmosphere most notably from the 1986 Chernobyl meltdown. It's because this isotope (137Cs) is one of the numerous products of fission, which directly issue from the fission of an Uranium core.
Beginning in 1945 with the commencement of nuclear testing, 137Cs was released into the atmosphere where it is absorbed readily into solution and is returned to the surface of the earth as a component of radioactive fallout. Once 137Cs enters the ground water, it is deposited on soil surfaces and removed from the landscape primarily by particle transport. As a result, the input function of these isotopes can be estimated as a function of time. Cesium-137 has a half-life of 30.17 years. It decomposes to Barium-137m (a short-lived product of decay) then to a form of nonradioactive Barium.
|Cs151||150.962||> 50 ms|
|All alkali metals are highly reactive. Cesium, being one of the heavier alkali metals, is also one of the most reactive and is highly explosive when it comes in contact with water (even cold water or ice). Cesium reacts violently with water and ice, forming cesium hydroxide (CsOH). Cesium hydroxide is the strongest base known and will attack glass.|
Cesium Hydroxide is an extremely strong base, and can etch glass.
|Cesium compounds are encountered rarely by most persons . All Cesium compounds should be regarded as mildly toxic because of its chemical similarity to Potassium.|
Large amounts cause hyperirritability and spasms, but such amounts would not ordinarily be encountered in natural sources, so Cs is not a major chemical environmental pollutant. Rats fed Cesium in place of Potassium in their diet 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 which varies depending on location. Radiocesium does not accumulate in the body as effectively as many other fission products (such as radioiodine and radiostrontium), which are actively accumulated by the body.
Atomic Radius (Å): 3.34Å
Electrochemical Equivalents: 4.9587 g/amp-hr
Atomic Mass Average: 132.9054
(L. caesius, sky blue) Cesium was discovered spectroscopically by Bunsen and Kirchhoff in 1860 in mineral water from Durkheim. Cersium, an alkali metal, occurs in lepidolite, pollucte (a hydrated silicate of aluminum and cesium), and in other sources. One of the world's richest sources of cesium is located at Bernic Lake, Manitoba. The deposits are estimated to contain 300,000 tons of pollucite, averaging 20% cesium. It can be isolated by electrolysis of the fused cyanide and by a number of other methods. Very pure, gas-free cesium can be prepared by thermal decomposition of cesium azide. The metal is characterized by a spectrum containing two bright lines in the blue along with several others in the red, yellow, and green. It is silvery white, soft, and ductile. It is the most electropositive and most alkaline element. Cesium, gallium, and mercury are the only three metals that are liquid at room temperature. Cesium reacts explosively with cold water, and reacts with ice at temperatures above -116oC. Cesium hydroxide, the strongest base known, attacks glass. Because of its great affinity for oxygen the metal is used as a "getter" in electron tubes. It is also used in photoelectric cells, as well as a catalyst in the hydrogenation of certain organic compounds. The metal has recently found application in ion propulsion systems. Cesium is used in atomic clocks, which are accurate to 5 s in 300 years. Its chief compounds are the chloride and the nitrate. Cesium has 32 isotopes (more than any element) with masses ranging from 114 to 145. The present price of cesium is about $30/g.
Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond