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Cs
in WebElements
in X-Ray info
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Cs, 55
cesium (English)
caesium, m. (French)
Cäsium, n. (German)
tsezij (Russian)
cesio (Spanish)
cesium, -et (Swedish)
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| Symbol, number | Cs, 55 (alkali metal), Group: 1; 1A |
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| Weight | 132.9054 |
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| Looks | ?? |
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| In Nature | ?? |
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| Discovered | 1860, by R Bunsen and G R Kirchoff (Germany) |
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| Name | ?? |
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| Density [kg/m3] | 1873 [293 K] (solid) 1843 [302 K] (liquid) |
| Molar volume | 70.96 cm3 |
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| Speed of sound | no data m/s |
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| Critical Temperature | 1938 K (1665 °C) |
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| Superconducting Temp. | no data K ( °C) |
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| Melting Temperature | 301.55 K (28.55 °C) Enthalpy: 65.90 kJ/mol |
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| Boiling Temperature | 951.6 K (678.6 °C) Enthalpy: 2.09 kJ/mol |
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| Atomizing | 76 kJ/mol |
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| Modulus [GPa] | 1.7 (Young) no data (rigid) 1.6 (bulk) |
| Poisson's ratio | no data |
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| Hardness | 0.2 (mineral) 0.14 MN/m2 (Brinell) no data MN/m2 (Vicker's) |
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| Optics | no data% (reflection) no data (refraction) |
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| Specific heat | ?? |
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| Heat vapor | ?? |
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| Heat fusion | ?? |
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| Electrical resistance | 20.0E-8 [293 K] Wm |
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| Thermal | Conductivity: 35.9 [300 K] W/Km Expansion: 97E-6 /K |
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| Configuration | ?? |
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| Crystal structure | ?? |
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| Spectral lines [nm] | 455.528 I, 460.376 II, 522.704 II, 592.563 II, 852.113 I, 895.347 I |
| Ionisation [kJ/mol] |
| M--> |
M+--> |
M2+--> |
M3+--> |
M4+--> |
M5+--> |
M6+--> |
M7+--> |
M8+--> |
M9+-->M10+ |
| 375.7 |
2420 |
(3400) |
(4400) |
(6000) |
(7100) |
(8300) |
(11300) |
(12700) |
(23700) |
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| Thermodynamics |
| State |
DfH° |
DfG° |
S° |
CpH |
H°298.15-H°0 |
| [kJ/mol] |
[J/Kmol] |
[kJ/mol] |
| Solid |
0 |
85.23±0.40 |
32.2 |
7.711±0.020 |
| Gas |
76.5±1.0 |
49.6 |
175.601±0.003 |
20.8 |
6.197±0.001 |
| Gas (Cs2) |
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284.6 |
38.3 |
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| Isotopes |
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Mass |
In nature |
Half-life |
Spin |
m/mN |
NMM |
Decay |
| 129Cs |
128.90606 |
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1.336 d |
1/2 |
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1.49 |
EC to 129Xe |
| 130Cs |
129.90671 |
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29.21 m |
1 |
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1.46 |
EC to 130Xe; β- to 130Ba |
| 131Cs |
130.90546 |
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9.69 d |
5/2 |
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3.54 |
EC to 131Xe |
| 132Cs |
131.906430 |
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6.48 d |
2 |
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2.22 |
EC to 132Xe; β- to 132Ba |
| 133Cs |
132.905429 |
100% |
stable |
7/2 |
2.582024 |
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| 134Cs |
133.906714 |
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2.065 d |
4 |
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2.994 |
EC to 134Xe; β- to 134Ba |
| 135Cs |
134.905972 |
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2.3E6 y |
7/2 |
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2.732 |
β- to 135Ba |
| 136Cs |
135.907307 |
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13.16 d |
5 |
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3.71 |
β- to 136Ba |
| 137Cs |
136.907085 |
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30.2 y |
7/2 |
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2.84 |
β- to 137Ba |
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