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[General | States | Energies | Oxidation & Electrons]
[Appearance & Characteristics | Reactions | Other Forms]
[Radius | Conductivity
| Abundance | History]
| Name |
Cesium |
Symbol |
Cs |
| Atomic number |
55 |
Atomic weight |
132.9054 |
| Density @ 293 K |
1.873 g/cm3 |
Atomic volume |
71.07 cm3/mol |
| Group |
Alkali Met. |
Discovered |
1860 |
| State (s, l, g) |
s |
| Melting point |
301.6 K |
Boiling point |
978 K |
| Heat of fusion |
2.092 kJ/mol |
Heat of vaporization |
67.740 kJ/mol |
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| 1st ionization energy |
375.7 kJ/mole |
Electronegativity |
0.79 |
| 2nd ionization energy |
2421.8 kJ/mole |
Electron affinity |
45.506 kJ/mole |
| 3rd ionization energy |
kJ/mole |
Specific heat |
0.24 J/gK |
| Heat atomization |
79 kJ/mole atoms |
| Shells |
2,8,18,18,8,1 |
Electron configuration |
[Xe] 6s1 |
| Minimum oxidation number |
0 |
Maximum oxidation number |
1 |
| Minimum common oxidation number |
0 |
Maximum common oxidation number |
1 |
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| Structure |
bcc: body-centered cubic |
Color |
yellow/silvery |
| Uses |
photocells, IR lamps |
Toxicity |
|
| Hardness |
0.2 mohs |
Characteristics |
softest metal |
| Reaction with air |
vigorous, =>CsO2 |
Reaction with 6M HCl |
vigorous, =>H2, CsCl |
| Reaction with 6M HCl |
vigorous, =>H2, CsCl |
Reaction with 15M HNO3 |
vigorous, =>CsNO3 |
| Reaction with 6M NaOH |
vigorous, =>H2, CsOH |
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| Number of isotopes |
1 |
Hydride(s) |
CsH |
| Oxide(s) |
Cs2O |
Chloride(s) |
CsCl |
| Ionic radius (2- ion) |
pm |
Ionic radius (1- ion) |
pm |
| Atomic radius |
265 pm |
Ionic radius (1+ ion) |
181 pm |
| Ionic radius (2+ ion) |
pm |
Ionic radius (3+ ion) |
pm |
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| Thermal conductivity |
35.9 J/m-sec-deg |
Electrical conductivity |
48.9 1/mohm-cm |
| Polarizability |
59.6 A^3 |
| Source |
Li extractn by-product |
Rel. abund. solar system |
-0.429 log |
| Abundance earth's crust |
0 log |
Cost, pure |
1100 $/100g |
| Cost, bulk |
$/100g |
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History:
(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. Cersium, 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
-116C. 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.
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