Elements
55

Cs

Caesium

Caesium (Cs) is a soft gray coloured metal that has the atomic number 55 in the periodic table. It is an Alkali Metal and is located in Group 1 of the periodic table. it has the symbol Cs.

Caesium was discovered in 1860 by Robert Bunsen and Gustav Kirchhoff whilst analysing the contents of mineral water using spectroscopy. They discovered some lines in one spectrum that did not correspond to any known previously. Like other Alkali metals Caesium has a violent reaction with water and oxygen so must be kept in oil or an inert environment. Caesium’s main use is in atomic clocks for accuracy in timing. It is also used as a catalyst in the hydrogenation of organic compounds. It is a solid metal at room temperature with a melting point of 28.4°c and a boiling point of 670°c. Caesium if found in minerals pollucite and lepidolite in the earth’s crust and is not found naturally.

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FAQ's

What is the Melting Point for Caesium?

Caesium has a Melting Point of 28.44°F, meaning at 28.44°F it will turn to a liquid.

What is the Boiling Point for Caesium?

Caesium has a Boiling Point of 671°F, meaning at 671°F it will turn to a Gas.

What is the Electronegativity of Caesium?

Caesium's Electronegativty is 0.79. Electronegativity is a measure of how strongly atoms attract bonding electrons to themselves.

What is the Heat of Vaporization of Caesium?

Caesium has a Heat of Vaporization of 67.74 kJ/mol.

Uses

Used as a 'getter' to remove air traces in vacuum and cathode-ray tubes. Also used in producing photoelectric devices and atomic clocks. Since it ionizes readily, it is used as an ion rocket motor propellant.

Sources

Found in pollucite [(Cs4Al4Si9O26).H2O] and as trace in lepidolite.

55
Protons
55
Electrons
78
Neutrons

Cs

Element Symbol
Cs
Atomic Weight
132.905
Atomic Number
55
State
Solid
Melting Point
Unknown
28.44
°C
Boiling Point
671
Unknown
°C
Heat of Vaporization
67.74
Unknown
kJ/mol
Crystal Structure
Cubic: Body centered
Thermoconductivity
0.359
Unknown
W/cmK
Shells
2,8,18,18,8,1
Group
Alkali Metal
Period
6
Block
S Block
Orbitals
[Xe] 6s1
Coefficient of Thermal Expansion
100 10^-6 K^-1
Covalent Radius
2.35 Å
Density at 293K
1.873 g/cm³
Electrical Conductivity
0.0489 10^6/cm ohm
First Ionization Potential
3.8939 V
Second Ionization Potential
25.10 V
Third Ionization Potential
--
Ionic Radius
1.74 (+1) Å
Oxydation States
1
Lattice Parameter
6.0797 Å
Lattice Parameter 2
--
Lattice Parameter 3
--
Pronounced

SEE-zi-em

Discovered by

Gustov Kirchoff, Robert Bunsen

Discovery date

1860

Orbital configuration
2,8,18,18,8,1

Download the Periodic Table

Explore Other Alkali Metals

85.468
37

Rb

Rubidium
39.098
19

K

Potassium
223
87

Fr

Francium
6.941
3

Li

Lithium
22.99
11

Na

Sodium
The alkali metals, found in group 1 of the periodic table (formally known as group IA), are so reactive that they are generally found in nature combined with other elements. The alkali metals are shiny, soft, highly reactive metals at standard temperature and pressure.
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