Caesium Element (Periodic Table)

Caesium
Caesium block

Caesium (Cs), also spelled as cesium in American English, is a chemical element of the periodic table, located in group 1 and period 6, and has the atomic number 55. It is a soft, silvery-gold alkali metal whose name comes from the Latin word “caesius” (which means sky blue).

In 1860, German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered caesium using the newly invented method of flame spectroscopy.[1] It is a relatively rare element, with a total abundance in the Earth’s crust of about 3 parts per million.

Caesium reacts spontaneously in the air, which makes it hard to handle. This highly reactive silvery metal melts just above room temperature at 28.5 ℃ (83.3 ℉). Due to its reactive nature, caesium is considered a hazardous material and must be stored and transported separately for safety reasons.

With a Pauling scale value of 0.79, it is the least electronegative element. It is one of the elements with the most isotopes, with 40 known isotopes ranging from Caesium-112 to Caesium-151.

group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
period
1 1
H
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Hydrogen
2
He
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Helium
2 3
Li
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Lithium
4
Be
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Beryllium
5
B
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Boron
6
C
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Carbon
7
N
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Nitrogen
8
O
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Oxygen
9
F
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Fluorine
10
Ne
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Neon
3 11
Na
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Sodium
12
Mg
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Magnesium
13
Al
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Aluminium
14
Si
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Silicon
15
P
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Phosphorus
16
S
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Sulfur
17
Cl
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Chlorine
18
Ar
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Argon
4 19
K
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Potassium
20
Ca
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Calcium
21
Sc
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Scandium
22
Ti
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Titanium
23
V
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Vanadium
24
Cr
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Chromium
25
Mn
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Manganese
26
Fe
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Iron
27
Co
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Cobalt
28
Ni
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Nickel
29
Cu
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Copper
30
Zn
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Zinc
31
Ga
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Gallium
32
Ge
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Germanium
33
As
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Arsenic
34
Se
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Selenium
35
Br
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Bromine
36
Kr
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Krypton
5 37
Rb
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Rubidium
38
Sr
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Strontium
39
Y
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Yttrium
40
Zr
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Zirconium
41
Nb
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Niobium
42
Mo
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Molybdenum
43
Tc
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Technetium
44
Ru
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Ruthenium
45
Rh
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Rhodium
46
Pd
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Palladium
47
Ag
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Silver
48
Cd
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Cadmium
49
In
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Indium
50
Sn
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Tin
51
Sb
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Antimony
52
Te
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Tellurium
53
I
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Iodine
54
Xe
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Xenon
6 55
Cs
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Caesium
56
Ba
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Barium
72
Hf
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Hafnium
73
Ta
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Tantalum
74
W
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Tungsten
75
Re
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Rhenium
76
Os
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Osmium
77
Ir
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Iridium
78
Pt
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Platinum
79
Au
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Gold
80
Hg
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Mercury
81
Tl
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Thallium
82
Pb
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Lead
83
Bi
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Bismuth
84
Po
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Polonium
85
At
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Astatine
86
Rn
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Radon
7 87
Fr
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Francium
88
Ra
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Radium
104
Rf
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Rutherfordium
105
Db
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Dubnium
106
Sg
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Seaborgium
107
Bh
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Bohrium
108
Hs
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Hassium
109
Mt
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Meitnerium
110
Ds
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Darmstadtium
111
Rg
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Roentgenium
112
Cn
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Copernicium
113
Nh
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Nihonium
114
Fl
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Flerovium
115
Mc
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Moscovium
116
Lv
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Livermorium
117
Ts
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Tennessine
118
Og
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Oganesson
57
La
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Lanthanum
58
Ce
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Cerium
59
Pr
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Praseodymium
60
Nd
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Neodymium
61
Pm
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Promethium
62
Sm
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Samarium
63
Eu
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Europium
64
Gd
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Gadolinium
65
Tb
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Terbium
66
Dy
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Dysprosium
67
Ho
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Holmium
68
Er
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Erbium
69
Tm
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Thulium
70
Yb
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Ytterbium
71
Lu
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Lutetium
89
Ac
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Actinium
90
Th
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Thorium
91
Pa
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Protactinium
92
U
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Uranium
93
Np
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Neptunium
94
Pu
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Plutonium
95
Am
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Americium
96
Cm
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Curium
97
Bk
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Berkelium
98
Cf
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Californium
99
Es
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Einsteinium
100
Fm
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Fermium
101
Md
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Mendelevium
102
No
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Nobelium
103
Lr
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Lawrencium
– s block

Caesium Element Information

Caesium Element
Caesium appearance | source: Wikipedia
Caesium Periodic Table
Caesium location on periodic table
Caesium is found in the first column of the periodic table below the rubidium element.
Origin of name Latin word “caesius” (which means sky blue)
Symbol Cs
Atomic number (Z) 55
Atomic mass 132.90545 u
Block s-block
Group 1
Period 6
Classification Alkali metal
Atomic radius 265 pm
Covalent radius 244±11 pm
Van der Waals radius 343 pm
Melting point 28.5 ℃, 83.3 ℉, 301.7 K
Boiling point 671 ℃, 1240 ℉, 944 K
Electron configuration [Xe] 6s1
Electrons per shell 2, 8, 18, 18, 8, 1
Learn how to draw: Caesium Bohr Model
Crystal structure Body-centered cubic (bcc)
Phase at r.t Solid
Density near r.t 1.93 g/cm3
Main isotopes Caesium-133
Natural occurrence Primordial
Oxidation state +1
Electronegativity (Pauling scale) 0.79
Protons
Neutrons
Electrons
55
78
55
Valence electrons 1
Learn how to find: Caesium Valence Electrons
CAS number 7440-46-2
Discovered by Robert Bunsen and Gustav Kirchhoff in 1860

How was Caesium discovered?

Gustav Kirchhoff (Left) And Robert Bunsen
Gustav Kirchhoff (left) and Robert Bunsen | source: Science History Institute

In 1860, Robert W. Bunsen and Gustav R. Kirchhoff were the first to discover the element caesium through spectroscopic means, using the spectroscope they had just invented the year before.

They attempted to create elemental caesium through the electrolysis of molten caesium chloride, but instead obtained a blue, homogeneous substance.

It was not until later, when German chemist Carl Setterberg at the University of Bonn electrolyzed caesium cyanide CsCN, that pure caesium metal was successfully isolated.

Caesium has traditionally been used mostly in research and development. Before the 1920s, it was primarily used in vacuum tubes as a “getter” to remove trace amounts of oxygen and other gasses that became trapped in the tube when it was sealed. Prior to this time, the element had no significant practical applications.[2]

How is Caesium produced?

Because caesium is naturally found combined with other alkali metals and always found with rubidium, producing pure caesium has a number of challenges.

Caesium has mostly been produced from its ore pollucite, using three methods: acid digestion, alkaline decomposition, and direct reduction.

Also, caesium metal can be produced from the ore’s purified compounds. Cesium chloride and other cesium halides can be reduced to caesium metal using calcium or barium at a temperature of 700 ℃ to 800 ℃. The resulting caesium metal can then be distilled and collected.

Properties of Caesium

Caesium is a metal that is known for its soft and ductile nature, as well as its low melting point of 28.5 ℃. Due to its extremely low melting point, it often exists as a liquid that looks similar to mercury. Actually, it is the only metal that has a melting point lower than caesium.[3]

Caesium is also highly reactive, making it the most electropositive and reactive of the alkali metals. It has a tendency to ignite spontaneously when exposed to air and reacts explosively when it comes into contact with water.

Due to its reactive nature, caesium, like rubidium, is typically stored and transported in dry mineral oil, dry saturated hydrocarbons, or in an inert atmosphere or vacuum sealed in a borosilicate glass ampoule. This helps to prevent any unintended reactions with the surrounding environment.

Where is Caesium found?

Caesium is found in small amounts, around 3 parts per million, in the Earth’s crust in the minerals pollucite, rhodizite, and lepidolite. It is more abundant than a few well-known metals like tungsten, antimony, and cadmium.

Despite being chemically similar to rubidium, it is 30 times less abundant than rubidium. Only a few minerals contain considerable amounts of caesium. These include several unusual types of beryl, avogadrite, and rhodizite.

Pollucite is the only economically significant source mineral for caesium.[2] The Tanco Mine in Manitoba, Canada is the leading and most abundant source of caesium in the world, with an estimated 350,000 metric tons of pollucite ore, representing over two-thirds of the global pollucite reserves.

Large pollucite deposits have also been discovered in Zimbabwe, as well as in lithium-bearing pegmatites in Bernic Lake in Manitoba, Canada.

What is Caesium Used for?

Since the 1990s, the most often utilized form of caesium is found in cesium formate brines, a high-density, low-viscosity fluid used in high-temperature, high-pressure oil and gas drilling.[4]

Caesium is used in atomic clocks. The element also plays a crucial role in GPS, cell phone transmissions, the Internet, and aircraft guidance systems.

Caesium is utilized in photoelectric cells, which turn sunlight into energy. Direct sunlight stimulates the electrons in caesium atoms, and in photoelectric cells, these electrons flow to produce an electric current.

Caesium-137 can be used to enhance specific qualities of different food products by sterilization, killing insect pests and bacteria without noticeably changing the temperature of the food.

Caesium is added as a carbonate in optical glass to improve stability and durability. Similar to rubidium, caesium has the potential to be used as an ion engine fuel.

Additionally, caesium is used as a getter in vacuum tubes, in cancer treatment, in lasers and fluorescent lamps, and its compounds are used as an oxidizer in infrared flares.

Interesting Facts about Caesium

Caesium was discovered using a flame emission spectroscopy method.

Caesium has a very low melting point that if you place it on your hand, it will melt.

Caesium reacts explosively with oxygen and water, so it is often stored in mineral oil or kerosene.

Along with francium, caesium is also the most reactive metal.

Caesium has only one stable isotope, 133Cs.

Caesium is the 47th most abundant element on earth.

Caesium is the most electropositive chemical element.

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Related:

More Elements:

s block
p block
d block
f block
Barium Aluminium Bohrium Actinium
Beryllium Antimony Cadmium Americium
Caesium Argon Chromium Berkelium
Calcium Arsenic Cobalt Californium
Francium Astatine Copernicium Cerium
Helium Bismuth Copper Curium
Hydrogen Boron Darmstadtium Dysprosium
Lithium Bromine Dubnium Einsteinium
Magnesium Carbon Gold Erbium
Potassium Chlorine Hafnium Europium
Radium Flerovium Hassium Fermium
Rubidium Fluorine Iridium Gadolinium
Sodium Gallium Iron Holmium
Strontium Germanium Lawrencium Lanthanum
Indium Lutetium Mendelevium
Iodine Manganese Neodymium
Krypton Meitnerium Neptunium
Lead Mercury Nobelium
Livermorium Molybdenum Plutonium
Moscovium Nickel Praseodymium
Neon Niobium Promethium
Nihonium Osmium Protactinium
Nitrogen Palladium Samarium
Oganesson Platinum Terbium
Oxygen Rhenium Thorium
Phosphorus Rhodium Thulium
Polonium Roentgenium Uranium
Radon Ruthenium Ytterbium
Selenium Rutherfordium
Silicon Scandium
Sulfur Seaborgium
Tellurium Silver
Tennessine Tantalum
Thallium Technetium
Tin Titanium
Xenon Tungsten
Vanadium
Yttrium
Zinc
Zirconium

References:

1. C&EN: IT’S ELEMENTAL: THE PERIODIC TABLE – CESIUM

2. Cesium_MCP.indd

3. Exploring chemical elements and their compounds

4. Mineral Resource of the Month: Cesium – EARTH Magazine

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