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.
Notable characteristics
The electromagnetic spectrum of caesium 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. Caesium is also the most electropositive and most alkaline of the stable chemical elements and also has the lowest ionization potential of all the elements, except for francium. Caesium 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 340 to 550 grams| title=Francium (Atomic Number 87), the Last Discovered Natural Element| first=Jean-Pierre| last=Adloff| coauthors=George B. Kauffman| accessdate=2006-05-16}} in the entire earth at one time, its abundance can be considered zero in practical terms.)
Along with gallium, francium and mercury, caesium is among the only metals that are liquid at or near room temperature. Caesium reacts explosively in cold water and also reacts with ice at temperatures above −116°C. Caesium hydroxide (CsOH) is a very strong base and will rapidly etch the surface of glass.
There is an account that caesium, reacting with fluorine, takes up more fluorine than it stoichometrically 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 oxidised further by fluorine and form traces of a higher fluoride such as CsF3, analogous to XeF2.
134Cs has been used in hydrology as a measure of caesium 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 in this function.
Like other group 1 elements, caesium has a great affinity for oxygen and is used as a "getter" in vacuum tubes.
Because of their high density, Caesium chloride solutions are commonly used in molecular biology for density gradient ultracentrifugation, primarily for the isolation of nucleic acids from biological samples.
More 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)
History
Caesium (Latincaesius meaning "sky blue") was spectroscopically discovered by Robert Bunsen and Gustav Kirchhoff in 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 caesium metal was produced in 1881. Historically, the most important use for caesium has been in research and development, primarily in chemical and electrical applications.
Occurrence
An alkali metal, caesium occurs in lepidolite, pollucite (hydrated silicate of aluminium and caesium) and within other sources. 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% caesium.
It can be isolated by electrolysis of fused cyanide and in a number of other ways.
Exceptionally pure and gas-free caesium can be made by the thermal decomposition of caesium azide.
The primary compounds of caesium are its chloride and its nitrate. The price of caesium in 1997 was about $US 30 per gram.
Caesium 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 the largest number of isotopes, it has only one naturally occurring stable isotope, 133Cs, the other isotopes (except for the isotopes noted on this page) 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 notably from the 1986 Chernobyl meltdown. Beginning in 1945 with the commencement of nuclear testing, 137Cs was released into the atmosphere where it is absorbed readily into solution. 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.
Precautions
All alkaline metals are highly reactive. Caesium, being one of the heavier alkalinemetals, is also one of the most reactive and is highly explosive in cold water. Caesium hydroxide is an extremely strong base, and can attack glass.
Caesium compounds are encountered rarely by most people. All caesium 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 caesium 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. Radiocaesium does not accumulate in the body as effectively as many other fission products (such as radioiodine and radiostrontium), which are actively accumlated by the body.
"Caesium".
