Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. 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 [102 °F]), francium (27 °C [81 °F]), mercury (−39 °C [−38 °F]), and gallium (30 °C [86 °F]). This element is most notably used in atomic clocks.
The variant spelling cesium is used especially in North American English, but caesium is the spelling used by the IUPAC.
Technical Data
Symbol |
Cs |
Density (25°C)/gcm-3 |
1.9 |
Atomic number |
55 |
Melting point / °C |
28.5 |
No. of naturally occurring isotopes |
1 |
Boiling point / °C |
705 |
Atomic weight |
132.9054 |
ΔHfus/kJmol-1 |
2.09 |
Electronic configuration |
[Xe] 6s1 |
ΔHvap/kJmol-1 |
67 |
Ionization energy/kJmol-1 |
375.6 |
ΔHf(monoatomic gas)/kJmol-1 |
79 |
Metal radius/pm |
265 |
Eo(M+(aq)+e- →M(S))/V |
-2.92 |
Ionic radius (6-coordinate)/pm |
167 |
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|
Evaporation Techniques
Temperature (oC) @Vap. Pressure |
Techniques |
Remarks |
10-8 Torr |
10-6 Torr |
10-4 Torr |
Electron Beam |
Crucible |
Coil |
Boat |
-16 |
+22 |
+30 |
- |
Quartz |
- |
Stainless Steel |
|