Cesium (Cs)

Cesium is the 55th element in the periodic table and has a symbol of Cs and atomic number of 55. It has an atomic weight of 132.90545 and a mass number of 133. Cesium has fifty-five protons and seventy-eight neutrons in its nucleus, and fifty-five electrons in six shells. It is located in group one, period six and block s of the periodic table. Soft silvery-white metallic element belonging to group 1 of the periodic table. One of the three metals which are liquid at room temperature. Cs-133 is the natural, and only stable, isotope. Fifteen other radioisotopes exist. Caesium reacts explosively with cold water, and ice at temperatures above 157K. Caesium hydroxide is the strongest base known. Caesium is the most electropositive, most alkaline and has the least ionization potential of all the elements. Known uses include the basis of atomic clocks, catalyst for the hydrogenation of some organic compounds, and in photoelectric cells. Caesium was discovered by Gustav Kirchoff and Robert Bunsen in Germany in 1860 spectroscopically. Its identification was based upon the bright blue lines in its spectrum. The name comes from the latin word caesius, which means sky blue. Caesium should be considered highly toxic. Some of the radioisotopes are even more toxic.

Atomic Number	55
Atomic Weight	132.90545196
Mass Number	133

Group	1
Period	6
Block	s

Protons	55 p⁺
Neutrons	78 n⁰
Electrons	55 e^-

Physical Properties

Atomic Radius	260 pm 249 pm
Molar Volume	70 cm³/mol
Covalent Radius	232 pm 209 pm 237 pm 244 pm
Metallic Radius	235 pm 267 pm
Ionic Radius	167 pm 174 pm 178 pm 181 pm 185 pm 188 pm
Crystal Radius	181 pm 188 pm 192 pm 195 pm 199 pm 202 pm
Van der Waals Radius	300 pm 343 pm 344 pm 343 pm 451.7 pm
Density	1.873 g/cm³ 1,843 kg/m³

Chemical Properties

Energy

Proton Affinity
Electron Affinity	0.471626 eV/particle
Ionization Energy	3.893905548 eV/particle 23.15745 eV/particle 33.195 eV/particle 43 eV/particle 56 eV/particle 69.1 eV/particle 82.9 eV/particle 110.09 eV/particle 125.61 eV/particle 213.3 eV/particle 233 eV/particle 261 eV/particle 289 eV/particle 316 eV/particle 352 eV/particle 382 eV/particle 413 eV/particle 445 eV/particle 476 eV/particle 597 eV/particle 629 eV/particle 666 eV/particle 700 eV/particle 753 eV/particle 791 eV/particle 875 eV/particle 916.07 eV/particle 1,592 eV/particle 1,672 eV/particle 1,757 eV/particle 1,848 eV/particle 1,936 eV/particle 2,029 eV/particle 2,137 eV/particle 2,230 eV/particle 2,329 eV/particle 2,422 eV/particle 2,683 eV/particle 2,767 eV/particle 2,859 eV/particle 2,945 eV/particle 3,118 eV/particle 3,214 eV/particle 3,392 eV/particle 3,485 eV/particle 7,989 eV/particle 8,224 eV/particle 8,484 eV/particle 8,726 eV/particle 9,350 eV/particle 9,629 eV/particle 9,974 eV/particle 10,208.78 eV/particle 41,861.073 eV/particle 42,912.99 eV/particle

Heat of Vaporization	68.3 kJ/mol
Heat of Fusion	2.09 kJ/mol
Heat of Formation	76.5 kJ/mol
Electrons

Electron Shells	2, 8, 18, 18, 8, 1

Valence Electrons	1 ⓘ

Electron Configuration	[Xe] 6s¹ⓘ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s¹

Oxidation States	-1, 1
Electronegativity	3.898 eV/particle 0.1542125 0.79
Electrophilicity Index	0.696095447101947 eV/particle
States of Matter

Phase	Solid
Gas Phase
Boiling Point	944.15 K
Melting Point	301.65 K
Critical Pressure	9.4 MPa
Critical Temperature	1,938.15 K
Triple Point
Visual
Cesium is a Silver. Cs has a CPK of #ff1493, Jmol of #57178f, and MOLCAS GV of #57178f. The Appearance of Element 55 is silvery gold.
Color	Silver #ff1493 #57178f #57178f
Appearance	silvery gold
Refractive Index
Thermodynamic Properties
Thermal Conductivity	35.9 W/(m K)
Thermal Expansion
Molar Heat Capacity	32.21 J/(mol K)
Specific Heat Capacity	0.242 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type	Conductor
Electrical Conductivity	5 MS/m
Electrical Resistivity	0.0000002 Ω*m
Superconducting Point
Magnetism
Type	paramagnetic
Magnetic Susceptibility (Mass)	0.0000000028 m³/Kg
Magnetic Susceptibility (Molar)	0.000000000372 m³/mol
Magnetic Susceptibility (Volume)	0.00000526
Magnetic Ordering
Curie Point
Neel Point
Structure
The Crystal Structure of Cesium is BCC. The lattice constant of Cs is 6.05 Å. The lattice angles of Element 55 are π/2, π/2, π/2.
Crystal Structure	Body Centered Cubic (BCC)
Lattice Constant	6.05 Å
Lattice Angles	π/2, π/2, π/2
Mechanical Properties
Cesium has a Brinell of 0.14 MPa, and Mohs hardness of 0.2 MPa. The Bulk Modulus of Cs is 1.6 GPa. The Young Modulus of Element 55 is 1.7 GPa.
Hardness	0.14 MPa 0.2 MPa
Bulk Modulus	1.6 GPa
Shear Modulus
Young's Modulus	1.7 GPa
Poisson Ratio
Speed of Sound
Classification
The CAS Group of Cesium is IA. The IUPAC Group of Cs is IA. The Glawe Number of Element 55 is 8. The Mendeleev Number of Cesium (Cs) is 5. The Pettifor Number of Cesium is 8. The Geochemical Class of Cs is alkali metal. The Goldschmidt Class of Element 55 is litophile.
Category	Alkali metals, Alkali metals
CAS Group	IA
IUPAC Group	IA
Glawe Number	8
Mendeleev Number	5
Pettifor Number	8
Geochemical Class	alkali metal
Goldschmidt Class	litophile

Other

The Dipole Polarizability of Cesium is 400.9 plus or minus 0.7 a₀. Cs has a C6 Dispersion Coefficient (GB) of 6660 a₀. The Allotropes of Element 55 is . The Neutron Cross Section of Cesium (Cs) is 29. The Neutron Mass Absorption of Cesium is 0.0077. The Quantum Numbers of Cs is 2S1/2. The Space Group of Element 55 is 229 (Im_3m).

Gas Basicity
Dipole Polarizability	400.9 ± 0.7 a₀
C6 Dispersion Coefficient	6,660 a₀
Allotropes
Neutron Cross Section	29
Neutron Mass Absorption	0.0077
Quantum Numbers	2S1/2
Space Group	229 (Im_3m)

Isotopes of Cesium

Stable Isotopes	1
Unstable Isotopes	41
Natural Isotopes	1

¹¹¹Cs

Mass Number	111
Neutron Number	56
Relative Atomic Mass	110.953945 ± 0.000215 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year
Parity	+

Decay Mode	Intensity
p (proton emission)

¹¹²Cs

Mass Number	112
Neutron Number	57
Relative Atomic Mass	111.950172 ± 0.000124 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	490 ± 30 us
Spin	1
Quadrupole Moment
Discovery Year	1994
Parity	+

Decay Mode	Intensity
p (proton emission)	100%
α (α emission)	0.26%

¹¹³Cs

Mass Number	113
Neutron Number	58
Relative Atomic Mass	112.944428484 ± 0.000009207 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	16.94 ± 0.09 us
Spin	3/2
Quadrupole Moment
Discovery Year	1984
Parity	+

Decay Mode	Intensity
p (proton emission)	100%

¹¹⁴Cs

Mass Number	114
Neutron Number	59
Relative Atomic Mass	113.941292244 ± 0.000091323 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	570 ± 20 ms
Spin	1
Quadrupole Moment
Discovery Year	1978
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	0.018%
β⁺ p (β⁺-delayed proton emission)	8.7%
β⁺α (β⁺-delayed α emission)	0.19%

¹¹⁵Cs

Mass Number	115
Neutron Number	60
Relative Atomic Mass	114.93591 ± 0.00011 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.4 ± 0.8 s
Spin	9/2
Quadrupole Moment
Discovery Year	1978
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	0.07%

¹¹⁶Cs

Mass Number	116
Neutron Number	61
Relative Atomic Mass	115.933395 ± 0.000108 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	700 ± 40 ms
Spin	1
Quadrupole Moment
Discovery Year	1975
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	0.28%
β⁺α (β⁺-delayed α emission)	0.049%

¹¹⁷Cs

Mass Number	117
Neutron Number	62
Relative Atomic Mass	116.928616723 ± 0.000067 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	8.4 ± 0.6 s
Spin	9/2
Quadrupole Moment
Discovery Year	1972
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹¹⁸Cs

Mass Number	118
Neutron Number	63
Relative Atomic Mass	117.926559517 ± 0.00001369 Da
G-Factor	1.935 ± 0.0025
Abundance
Radioactivity	☢️ Radioactive
Half Life	14 ± 2 s
Spin	2
Quadrupole Moment	1.31 ± 0.17
Discovery Year	1969
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	0.021%
β⁺α (β⁺-delayed α emission)	0.0012%

¹¹⁹Cs

Mass Number	119
Neutron Number	64
Relative Atomic Mass	118.922377327 ± 0.000014965 Da
G-Factor	1.2111111111111 ± 0.0066666666666667
Abundance
Radioactivity	☢️ Radioactive
Half Life	43 ± 0.2 s
Spin	9/2
Quadrupole Moment	2.65 ± 0.17
Discovery Year	1969
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺α (β⁺-delayed α emission)	2%

¹²⁰Cs

Mass Number	120
Neutron Number	65
Relative Atomic Mass	119.920677277 ± 0.000010702 Da
G-Factor	1.93 ± 0.01
Abundance
Radioactivity	☢️ Radioactive
Half Life	60.4 ± 0.6 s
Spin	2
Quadrupole Moment	1.36 ± 0.07
Discovery Year	1969
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺α (β⁺-delayed α emission)	2%
β⁺ p (β⁺-delayed proton emission)	7%

¹²¹Cs

Mass Number	121
Neutron Number	66
Relative Atomic Mass	120.917227235 ± 0.00001534 Da
G-Factor	0.51266666666667 ± 0.0026666666666667
Abundance
Radioactivity	☢️ Radioactive
Half Life	155 ± 4 s
Spin	3/2
Quadrupole Moment	0.79 ± 0.04
Discovery Year	1969
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹²²Cs

Mass Number	122
Neutron Number	67
Relative Atomic Mass	121.916108144 ± 0.000036164 Da
G-Factor	0.133 ± 0.002
Abundance
Radioactivity	☢️ Radioactive
Half Life	21.18 ± 0.19 s
Spin	1
Quadrupole Moment	-0.179 ± 0.01
Discovery Year	1969
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺α (β⁺-delayed α emission)	2%

¹²³Cs

Mass Number	123
Neutron Number	68
Relative Atomic Mass	122.91299606 ± 0.000013 Da
G-Factor	2.75 ± 0.014
Abundance
Radioactivity	☢️ Radioactive
Half Life	5.88 ± 0.03 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1954
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹²⁴Cs

Mass Number	124
Neutron Number	69
Relative Atomic Mass	123.912247366 ± 0.000009823 Da
G-Factor	0.672 ± 0.003
Abundance
Radioactivity	☢️ Radioactive
Half Life	30.9 ± 0.4 s
Spin	1
Quadrupole Moment	-0.69 ± 0.04
Discovery Year	1969
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹²⁵Cs

Mass Number	125
Neutron Number	70
Relative Atomic Mass	124.909725953 ± 0.000008304 Da
G-Factor	2.814 ± 0.014
Abundance
Radioactivity	☢️ Radioactive
Half Life	44.35 ± 0.29 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1954
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹²⁶Cs

Mass Number	126
Neutron Number	71
Relative Atomic Mass	125.909445821 ± 0.00001112 Da
G-Factor	0.776 ± 0.004
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.64 ± 0.02 m
Spin	1
Quadrupole Moment	-0.64 ± 0.03
Discovery Year	1954
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹²⁷Cs

Mass Number	127
Neutron Number	72
Relative Atomic Mass	126.907417527 ± 0.000005987 Da
G-Factor	2.914 ± 0.014
Abundance
Radioactivity	☢️ Radioactive
Half Life	6.25 ± 0.1 h
Spin	1/2
Quadrupole Moment	0
Discovery Year	1950
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹²⁸Cs

Mass Number	128
Neutron Number	73
Relative Atomic Mass	127.907748452 ± 0.000005771 Da
G-Factor	0.972 ± 0.005
Abundance
Radioactivity	☢️ Radioactive
Half Life	3.64 ± 0.014 m
Spin	1
Quadrupole Moment	-0.54 ± 0.03
Discovery Year	1951
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹²⁹Cs

Mass Number	129
Neutron Number	74
Relative Atomic Mass	128.90606591 ± 0.000004888 Da
G-Factor	2.978 ± 0.016
Abundance
Radioactivity	☢️ Radioactive
Half Life	32.06 ± 0.06 h
Spin	1/2
Quadrupole Moment	0
Discovery Year	1950
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹³⁰Cs

Mass Number	130
Neutron Number	75
Relative Atomic Mass	129.906709281 ± 0.000008971 Da
G-Factor	1.458 ± 0.007
Abundance
Radioactivity	☢️ Radioactive
Half Life	29.21 ± 0.04 m
Spin	1
Quadrupole Moment	-0.056 ± 0.006
Discovery Year	1952
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	98.4%
β⁻ (β⁻ decay)	1.6%

¹³¹Cs

Mass Number	131
Neutron Number	76
Relative Atomic Mass	130.905468457 ± 0.00000019 Da
G-Factor	1.4144 ± 0.0012
Abundance
Radioactivity	☢️ Radioactive
Half Life	9.689 ± 0.016 d
Spin	5/2
Quadrupole Moment	0.59 ± 0.02
Discovery Year	1947
Parity	+

Decay Mode	Intensity
ϵ (electron capture)	100%

¹³²Cs

Mass Number	132
Neutron Number	77
Relative Atomic Mass	131.90643774 ± 0.000001112 Da
G-Factor	1.1095 ± 0.0035
Abundance
Radioactivity	☢️ Radioactive
Half Life	6.48 ± 0.006 d
Spin	2
Quadrupole Moment	0.48 ± 0.02
Discovery Year	1953
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	98.13%
β⁻ (β⁻ decay)	1.87%

¹³³Cs

Mass Number	133
Neutron Number	78
Relative Atomic Mass	132.905451958 ± 0.000000008 Da
G-Factor	0.73651428571429 ± 0.0004
Abundance	100
Radioactivity	Stable
Half Life	Not Radioactive ☢️
Spin	7/2
Quadrupole Moment	-0.00343 ± 0.0001
Discovery Year	1921
Parity	+

¹³⁴Cs

Mass Number	134
Neutron Number	79
Relative Atomic Mass	133.906718501 ± 0.000000017 Da
G-Factor	0.747325 ± 0.00035
Abundance
Radioactivity	☢️ Radioactive
Half Life	2.065 ± 0.0004 y
Spin	4
Quadrupole Moment	0.37 ± 0.02
Discovery Year	1940
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
ϵ (electron capture)	0.0003%

¹³⁵Cs

Mass Number	135
Neutron Number	80
Relative Atomic Mass	134.905976907 ± 0.00000039 Da
G-Factor	0.77951428571429 ± 0.00037142857142857
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.33 ± 0.19 My
Spin	7/2
Quadrupole Moment	0.048 ± 0.003
Discovery Year	1949
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

¹³⁶Cs

Mass Number	136
Neutron Number	81
Relative Atomic Mass	135.907311431 ± 0.00000201 Da
G-Factor	0.741 ± 0.003
Abundance
Radioactivity	☢️ Radioactive
Half Life	13.01 ± 0.05 d
Spin	5
Quadrupole Moment	0.213 ± 0.015
Discovery Year	1951
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

¹³⁷Cs

Mass Number	137
Neutron Number	82
Relative Atomic Mass	136.907089296 ± 0.000000324 Da
G-Factor	0.81068571428571 ± 0.0004
Abundance
Radioactivity	☢️ Radioactive
Half Life	30.04 ± 0.04 y
Spin	7/2
Quadrupole Moment	0.048 ± 0.002
Discovery Year	1951
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

¹³⁸Cs

Mass Number	138
Neutron Number	83
Relative Atomic Mass	137.911017119 ± 0.000009831 Da
G-Factor	0.233 ± 0.0013333333333333
Abundance
Radioactivity	☢️ Radioactive
Half Life	33.5 ± 0.2 m
Spin	3
Quadrupole Moment	0.112 ± 0.017
Discovery Year	1943
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

¹³⁹Cs

Mass Number	139
Neutron Number	84
Relative Atomic Mass	138.913363822 ± 0.000003364 Da
G-Factor	0.768 ± 0.0011428571428571
Abundance
Radioactivity	☢️ Radioactive
Half Life	9.27 ± 0.05 m
Spin	7/2
Quadrupole Moment	-0.063 ± 0.014
Discovery Year	1939
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

¹⁴⁰Cs

Mass Number	140
Neutron Number	85
Relative Atomic Mass	139.917283707 ± 0.000008801 Da
G-Factor	0.134 ± 0.001
Abundance
Radioactivity	☢️ Radioactive
Half Life	63.7 ± 0.3 s
Spin	1
Quadrupole Moment	-0.094 ± 0.015
Discovery Year	1950
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

¹⁴¹Cs

Mass Number	141
Neutron Number	86
Relative Atomic Mass	140.920045279 ± 0.000009871 Da
G-Factor	0.69457142857143 ± 0.0028571428571429
Abundance
Radioactivity	☢️ Radioactive
Half Life	24.84 ± 0.16 s
Spin	7/2
Quadrupole Moment	-0.42 ± 0.07
Discovery Year	1962
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	0.0342%

¹⁴²Cs

Mass Number	142
Neutron Number	87
Relative Atomic Mass	141.924299514 ± 0.000007586 Da
G-Factor	0
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.687 ± 0.01 s
Spin	0
Quadrupole Moment	0
Discovery Year	1962
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	0.089%

¹⁴³Cs

Mass Number	143
Neutron Number	88
Relative Atomic Mass	142.927347346 ± 0.00000813 Da
G-Factor	0.57933333333333 ± 0.0026666666666667
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.802 ± 0.008 s
Spin	3/2
Quadrupole Moment	0.44 ± 0.03
Discovery Year	1962
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	1.62%

¹⁴⁴Cs

Mass Number	144
Neutron Number	89
Relative Atomic Mass	143.932075402 ± 0.000021612 Da
G-Factor	-0.545 ± 0.003
Abundance
Radioactivity	☢️ Radioactive
Half Life	994 ± 6 ms
Spin	1
Quadrupole Moment	0.29 ± 0.02
Discovery Year	1967
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	2.98%

¹⁴⁵Cs

Mass Number	145
Neutron Number	90
Relative Atomic Mass	144.935528927 ± 0.000009733 Da
G-Factor	0.522 ± 0.0026666666666667
Abundance
Radioactivity	☢️ Radioactive
Half Life	582 ± 4 ms
Spin	3/2
Quadrupole Moment	0.58 ± 0.06
Discovery Year	1971
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	12.8%

¹⁴⁶Cs

Mass Number	146
Neutron Number	91
Relative Atomic Mass	145.940621867 ± 0.000003106 Da
G-Factor	-0.514 ± 0.002
Abundance
Radioactivity	☢️ Radioactive
Half Life	321.6 ± 0.9 ms
Spin	1
Quadrupole Moment	0.21 ± 0.03
Discovery Year	1971
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	14.2%
2n (2-neutron emission)

¹⁴⁷Cs

Mass Number	147
Neutron Number	92
Relative Atomic Mass	146.944261512 ± 0.000009 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	230.5 ± 0.9 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1978
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	28.5%

¹⁴⁸Cs

Mass Number	148
Neutron Number	93
Relative Atomic Mass	147.949639026 ± 0.000014 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	151.8 ± 1 ms
Spin	2
Quadrupole Moment
Discovery Year	1978
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	28.7%
2n (2-neutron emission)

¹⁴⁹Cs

Mass Number	149
Neutron Number	94
Relative Atomic Mass	148.953516 ± 0.000429 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	112.3 ± 2.5 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1979
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	25%
2n (2-neutron emission)

¹⁵⁰Cs

Mass Number	150
Neutron Number	95
Relative Atomic Mass	149.959023 ± 0.000429 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	81 ± 2.6 ms
Spin	2
Quadrupole Moment
Discovery Year	1979
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	44%
2n (2-neutron emission)

¹⁵¹Cs

Mass Number	151
Neutron Number	96
Relative Atomic Mass	150.963199 ± 0.000537 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	59 ± 19 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1979
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)
2n (2-neutron emission)

¹⁵²Cs

Mass Number	152
Neutron Number	97
Relative Atomic Mass	151.968728 ± 0.000537 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life
Spin
Quadrupole Moment
Discovery Year	1987
Parity

Decay Mode	Intensity
β⁻ (β⁻ decay)
β⁻ n (β⁻-delayed neutron emission)

History

Robert Bunsen and Gustav Kirchhoff were the first to suggest finding cesium in 1860 by spectrum analysis. They discovered cesium by its two blue emission lines in a sample of Dürkheim mineral water. The pure metal was eventually isolated by the German chemist Carl Setterberg while working on his doctorate with Kekulé and Bunsen. From the Latin word caesius, sky blue

Discoverers	Gustov Kirchoff, Robert Bunsen
Discovery Location	Germany
Discovery Year	1860
Etymology (Name Origin)	Latin: coesius (sky blue); for the blue lines of its spectrum.
Pronunciation	SEE-zi-em (English)

Cesium compounds are considered to be mildly toxic

Cesium was the first element discovered using a spectroscope

Uses

The radioactive isotope cesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Cesium is also used in photoelectric cells and as a catalyst in the hydrogenation of organic compounds. Cesium vapor thermionic generators are low-power devices that convert heat energy to electrical energy. 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.

Abundance
Abundance in Earth's crust	3 mg/kg
Natural Abundance (Oceans)	0.0003 mg/L
Natural Abundance (Human Body)	0.000002 %
Natural Abundance (Meteor)	0.000014 %
Natural Abundance (Sun)	0.0000008 %
Abundance in Universe	0.00000008 %

Nuclear Screening Constants

1	s	1.0957
2	p	4.1804
2	s	14.4884
3	d	14.0194
3	p	18.4222
3	s	18.6226
4	d	32.1616
4	p	29.1424
4	s	27.9576
5	p	41.349
5	s	39.5555
6	s	48.637

Also Known As

Cs
element 55
55Cs
cæsium
cesium

Translations

Norwegian Bokmålcesium
Frenchcésium
Italiancesio
Russianцезий
Norwegian Nynorskcesium
Swedishcesium
Danishcæsium
GermanCaesium
Hungariancézium
Spanishcesio
Afrikaanssesium
Amharicሴሲየም
AragoneseCesio
Arabicسيزيوم
AzerbaijaniSezium
BelarusianЦэзій
Bulgarianцезий
Banglaসিজিয়াম
BretonKeziom
Bosniancezij
Catalancesi
CorsicanCesiu
Czechcesium
ChuvashЦези
WelshCesiwm
Greekκαίσιο
Esperantocezio
EstonianTseesium
Basquezesio
Persianسزیم
Finnishcesium
FriulianCesi
IrishCaeisiam
Galiciancesio
ManxKaishum
Hakka Chinesecaesium
Hebrewצסיום
Hindiसीज़ियम
Fiji HindiCaesium
CroatianCezij
Haitian CreoleSezyòm
Armenianցեզիում
Interlinguacesium
Indonesiansesium
Idocesio
Icelandicsesín
Japaneseセシウム
Lojbanblasodna
Georgianცეზიუმი
KazakhЦезий
Kannadaಸೀಸಿಯಮ್
Korean세슘
KurdishSezyûm
KomiЦезий
Latincaesium
LuxembourgishCäsium
LigurianÇesio
LithuanianCezis
Latviancēzijs
Macedonianцезиум
Malayalamസീസിയം
Marathiसिझियम
Western MariЦезий
MalaySesium
Burmeseဆယ်ဆီယမ်
Low GermanCäsium
Dutchcesium
OccitanCèsi
Polishcez
Western Panjabiسیزیم
Portuguesecésio
QuechuaSesyu
Romaniancesiu
YakutСезиум
Siciliancesiu
Serbo-CroatianCezijum
Slovakcézium
SlovenianCezij
AlbanianCeziumi
Serbianцезијум
Saterland FrisianCesium
SwahiliCaesi
Tamilசீசியம்
Teluguసీసియం
Thaiซีเซียม
TagalogSesyo
TurkishSezyum
Uyghurسېزىي
Ukrainianцезій
Urduسیزیئم
VepsCezii
Vietnamesexêsi
WalloonCeziom
WarayCesyo
KalmykЦесиүм
Yiddishצעז
YorubaKesium
Chinese铯
JavaneseSesium
Punjabiਸੀਜ਼ੀਅਮ
CebuanoCesyo
Central Kurdishسیزیۆم
Odiaସିଜିଅମ
Gujaratiસીસીયમ
Scotscaesium
Tatarцезий
PiedmonteseCesio
SomaliKaasiyaam
Literary Chinese銫
Cantonese銫
Belarusian (Taraskievica orthography)цэз
UzbekSeziy
AromanianCesiu
KyrgyzЦезий
LimburgishCesium
Malteseċesju
LombardCesio
Scottish GaelicCaesium
Bhojpuriसीजियम
Sanskritसेसियम
Nepaliसिजियम
Paliसेसियम
Newariसेसियम
Gan Chinese銫
Mongolianцези
cdoCaesium
Min Nan ChineseCaesium
FaroeseSesium
Tibetanསྰེ་སིམ།
AsturianCesiu
BavarianZäsium
Portuguese (Brazil)césio
Tajikцезий
Tatar (Cyrillic)цезий
Wu Chinese铯
kbpSɛzɩyɔm
Lingua Franca Novasesio
oloCezii
Northern FrisianTseesium
Chinese (Traditional)銫
Chinese (Taiwan)銫
Chinese (Simplified)铯
SardinianTzèsiu
English (United Kingdom)caesium
BashkirЦезий
Moroccan Arabicسيزيوم
Egyptian Arabicسيزيوم
Pashtoسېزيوم
BikolSesyo
CornishCesiom
BalineseSésium
English (United States)cesium
GandaSeziyaamu
Korean (North Korea)세시움
ZuluUmCanga

Cesium on ChemicalAid

AGROVOC ID	c_1182
Art & Architecture Thesaurus ID	300380498
Australian Educational Vocabulary ID	scot/3063
BNCF Thesaurus ID	22890
Bibliothèque nationale de France ID	121655651
Brockhaus Enzyklopädie online ID	cäsium
CAB ID	18776
CAS Registry Number	7440-46-2
Cannabis Database ID	006361
ChEBI ID	30514
ChemSpider ID	4510778
Common Procurement Vocabulary	14771000
DSSTOX compound identifier	DTXCID40820345
DSSTox substance ID	DTXSID5036767
Den Store Danske ID	cæsium
DrugBank ID	15392
ECHA Substance Infocard ID	100.028.323
Encyclopædia Britannica Online ID	science/cesium
Encyclopædia Universalis ID	cesium
Freebase ID	/m/025tnb6
French Vikidia ID	Césium
GND ID	4147131-3
Gran Enciclopèdia Catalana ID	0090224
Great Russian Encyclopedia Online ID	4674014
HSDB ID	7040
Hrvatska enciklopedija ID	11373
Human Metabolome Database ID	HMDB0013669
InChI	InChI=1S/Cs
InChIKey	TVFDJXOCXUVLDH-UHFFFAOYSA-N
KBpedia ID	Cesium
Krugosvet article	himiya/ceziy
Library of Congress authority ID	sh85022200
MeSH descriptor ID	D002586
NDL Authority ID	00570840
NE.se ID	cesium
NKCR AUT ID	ph124977
National Library of Israel J9U ID	987007284955105171
OmegaWiki Defined Meaning	470
OpenAlex ID	C519659679
PSH ID	5748
PubChem CID	5354618
Quora topic ID	Cesium
RxNorm ID	1310121
Store norske leksikon ID	cesium
Treccani ID	cesio
UNII	1KSV9V4Y4I
USGS Thesaurus ID	1424
WordNet 3.1 Synset ID	14658410-n
YSO ID	16504
ZVG number	7550

Cesium (Cs)

Physical Properties

Chemical Properties

Other

Isotopes of Cesium

111Cs

112Cs

113Cs

114Cs

115Cs

116Cs

117Cs

118Cs

119Cs

120Cs

121Cs

122Cs

123Cs

124Cs

125Cs

126Cs

127Cs

128Cs

129Cs

130Cs

131Cs

132Cs

133Cs

134Cs

135Cs

136Cs

137Cs

138Cs

139Cs

140Cs

141Cs

142Cs

143Cs

144Cs

145Cs

146Cs

147Cs

148Cs

149Cs

150Cs

151Cs

152Cs