Cesium Element Information, Facts, Properties, Trends, Uses, Comparison with other elements
Caesium or cesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold Alkali Metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium is an Alkali Metal and has physical and chemical properties similar to those of rubidium and potassium.
It belongs to group 1 of the periodic table having trivial name alkali metals*. You can also download Printable Periodic Table of Elements Flashcards for Cesium in a PDF format.
Cesium Facts
Read key information and facts about element Cesium
| Name | Cesium |
| Atomic Number | 55 |
| Atomic Symbol | Cs |
| Atomic Weight | 132.90545 |
| Phase | Solid |
| Color | Silver |
| Appearance | silvery gold |
| Classification | Alkali Metal |
| Natural Occurance | Primordial |
| Group in Periodic Table | 1 |
| Group Name | lithium family |
| Period in Periodic Table | period 6 |
| Block in Periodic Table | s-block |
| Electronic Configuration | [Xe] 6s1 |
| Electronic Shell Structure (Electrons per shell) | 2, 8, 18, 18, 8, 1 |
| Melting Point | 301.59 K |
| Boiling Point | 944 K |
| CAS Number | CAS7440-46-2 |
How to Locate Cesium on Periodic Table
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 55 to find Cesium on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Cesium on periodic table look for cross section of group 1 and period 6 in the modern periodic table.
Cesium History
The element Cesium was discovered by R. Bunsen and R. Kirchhoff in year 1860 in Germany. Cesium was first isolated by C. Setterberg in 1882. Cesium derived its name from the Latin caesius, meaning 'sky blue'.
| Discovered By | R. Bunsen and R. Kirchhoff |
| Discovery Date | 1860 in Germany |
| First Isolation | 1882 |
| Isolated by | C. Setterberg |
Bunsen and Kirchhoff were the first to suggest finding new elements byspectrum analysis. They discovered caesium by its two blueemission linesin a sample ofDürkheimmineral water. The pure metal was eventually isolated in 1882 by Setterberg.
Cesium Uses
Caesium is used in vacuum tubes to remove trace gasses. Its major use is as a compound in drilling fluid. One of its most important uses is in the ‘caesium clock’ (atomic clock) and as a catalyst for the process of hydrogenation.
Cesium Presence: Abundance in Nature and Around Us
The table below shows the abundance of Cesium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
| ppb by weight (1ppb =10^-7 %) | ppb by atoms (1ppb =10^-7 %) | |
|---|---|---|
| Abundance in Universe | 0.8 | 0.01 |
| Abundance in Sun | 8 | 0.07 |
| Abundance in Meteorites | 140 | 20 |
| Abundance in Earth's Crust | 1900 | 290 |
| Abundance in Oceans | 0.5 | 0.023 |
| Abundance in Humans | 20 | 1 |
Crystal Structure of Cesium
The solid state structure of Cesium is Body Centered Cubic.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
Unit Cell Parameters
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
| a | b | c |
|---|---|---|
| 614.1 pm | 614.1 pm | 614.1 pm |
and the angles between them Lattice Angles (alpha, beta and gamma).
| alpha | beta | gamma |
|---|---|---|
| π/2 | π/2 | π/2 |
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
| Space Group Name | Im_ 3m |
| Space Group Number | 229 |
| Crystal Structure | Body Centered Cubic |
| Number of atoms per unit cell | 2 |
The number of atoms per unit cell in a simple cubic, face-centered cubic and body-centred cubic are 1,4,2 respectively.
Cesium Atomic and Orbital Properties
Cesium atoms have 55 electrons and the electronic shell structure is [2, 8, 18, 18, 8, 1] with Atomic Term Symbol (Quantum Numbers) 2S1/2.
| Atomic Number | 55 |
| Number of Electrons (with no charge) | 55 |
| Number of Protons | 55 |
| Mass Number | 133 |
| Number of Neutrons | 78 |
| Shell structure (Electrons per energy level) | 2, 8, 18, 18, 8, 1 |
| Electron Configuration | [Xe] 6s1 |
| Valence Electrons | 6s1 |
| Valence (Valency) | 1 |
| Main Oxidation States | 1 |
| Oxidation States | -1, 1 |
| Atomic Term Symbol (Quantum Numbers) | 2S1/2 |
Bohr Atomic Model of Cesium - Electrons per energy level
| n | s | p | d | f |
|---|
Ground State Electronic Configuration of Cesium - neutral Cesium atom
Abbreviated electronic configuration of Cesium
The ground state abbreviated electronic configuration of Neutral Cesium atom is [Xe] 6s1. The portion of Cesium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Xe]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 6s1, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Cesium
Complete ground state electronic configuration for the Cesium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s1
Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.
As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.
Hund's rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.
Atomic Structure of Cesium
Cesium atomic radius is 298 pm, while it's covalent radius is 225 pm.
| Atomic Radius Calculated | 298 pm(2.98 Å) |
| Atomic Radius Empirical | 260 pm (2.6 Å) |
| Atomic Volume | 70.732 cm3/mol |
| Covalent Radius | 225 pm (2.25 Å) |
| Van der Waals Radius | 343 pm |
| Neutron Cross Section | 29 |
| Neutron Mass Absorption | 0.0077 |
Spectral Lines of Cesium - Atomic Spectrum of Cesium
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules.
Spectral lines are the result of interaction between a quantum system and a single photon. A spectral line may be observed either as an emission line or an absorption line.
Spectral lines are highly atom-specific, and can be used to identify the chemical composition of any medium. Several elements, including helium, thallium, and caesium, were discovered by spectroscopic means. They are widely used to determine the physical conditions of stars and other celestial bodies that cannot be analyzed by other means.
Emission spectrum of Cesium
Absorption spectrum of Cesium
Absorption spectrum of Cesium is not available
Cesium Chemical Properties: Cesium Ionization Energies and electron affinity
The electron affinity of Cesium is 45.5 kJ/mol.
| Valence | 1 |
| Electronegativity | 0.79 |
| ElectronAffinity | 45.5 kJ/mol |
Ionization Energy of Cesium
Ionization energy is the amount of energy required to remove an electron from an atom or molecule.in chemistry, this energy is expresed in kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol).
Refer to table below for Ionization energies of Cesium
| Ionization energy number | Enthalpy - kJ/mol |
|---|---|
| 1st | 375.7 |
| 2nd | 2234.3 |
| 3rd | 3400 |
Cesium Physical Properties
Refer to below table for Cesium Physical Properties
| Density | 1.879 g/cm3(when liquid at m.p density is $1.843 g/cm3) |
| Molar Volume | 70.732 cm3/mol |
Elastic Properties
| Young Modulus | 1.7 |
| Shear Modulus | - |
| Bulk Modulus | 1.6 GPa |
| Poisson Ratio | - |
Hardness of Cesium - Tests to Measure of Hardness of Element
| Mohs Hardness | 0.2 MPa |
| Vickers Hardness | - |
| Brinell Hardness | 0.14 MPa |
Cesium Electrical Properties
Electrical resistivity measures element's electrical resistance or how strongly it resists electric current.The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). While Electrical conductivity is the reciprocal of electrical resistivity. It represents a element's ability to conduct electric current. The SI unit of electrical conductivity is siemens per metre (S/m).
Cesium is a conductor of electricity. Refer to table below for the Electrical properties of Cesium
| Electrical conductors | Conductor |
| Electrical Conductivity | 5000000 S/m |
| Resistivity | 2e-7 m Ω |
| Superconducting Point | - |
Cesium Heat and Conduction Properties
| Thermal Conductivity | 36 W/(m K) |
| Thermal Expansion | - |
Cesium Magnetic Properties
| Magnetic Type | Paramagnetic |
| Curie Point | - |
| Mass Magnetic Susceptibility | 2.8e-9 m3/kg |
| Molar Magnetic Susceptibility | 3.72e-10 m3/mol |
| Volume Magnetic Susceptibility | 0.00000526 |
Optical Properties of Cesium
| Refractive Index | - |
Acoustic Properties of Cesium
| Speed of Sound | - |
Cesium Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Cesium
| Melting Point | 301.59 K(28.44 °C, 83.192 °F) |
| Boiling Point | 944 K(670.85 °C, 1239.530 °F) |
| Critical Temperature | 1938 K |
| Superconducting Point | - |
Enthalpies of Cesium
| Heat of Fusion | 2.09 kJ/mol |
| Heat of Vaporization | 65 kJ/mol |
| Heat of Combustion | - |
Cesium Isotopes - Nuclear Properties of Cesium
Cesium has 40 isotopes, with between 112 and 151 nucleons. Cesium has 1 stable naturally occuring isotopes.
Isotopes of Cesium - Naturally occurring stable Isotopes: 133Cs.
| Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
|---|---|---|---|---|---|---|
| 112Cs | 55 | 57 | 112 | Synthetic | ||
| 113Cs | 55 | 58 | 113 | Synthetic | ||
| 114Cs | 55 | 59 | 114 | Synthetic | ||
| 115Cs | 55 | 60 | 115 | Synthetic | ||
| 116Cs | 55 | 61 | 116 | Synthetic | ||
| 117Cs | 55 | 62 | 117 | Synthetic | ||
| 118Cs | 55 | 63 | 118 | Synthetic | ||
| 119Cs | 55 | 64 | 119 | Synthetic | ||
| 120Cs | 55 | 65 | 120 | Synthetic | ||
| 121Cs | 55 | 66 | 121 | Synthetic | ||
| 122Cs | 55 | 67 | 122 | Synthetic | ||
| 123Cs | 55 | 68 | 123 | Synthetic | ||
| 124Cs | 55 | 69 | 124 | Synthetic | ||
| 125Cs | 55 | 70 | 125 | Synthetic | ||
| 126Cs | 55 | 71 | 126 | Synthetic | ||
| 127Cs | 55 | 72 | 127 | Synthetic | ||
| 128Cs | 55 | 73 | 128 | Synthetic | ||
| 129Cs | 55 | 74 | 129 | Synthetic | ||
| 130Cs | 55 | 75 | 130 | Synthetic | ||
| 131Cs | 55 | 76 | 131 | Synthetic | ||
| 132Cs | 55 | 77 | 132 | Synthetic | ||
| 133Cs | 55 | 78 | 133 | 100% | Stable | |
| 134Cs | 55 | 79 | 134 | Synthetic | ||
| 135Cs | 55 | 80 | 135 | Synthetic | ||
| 136Cs | 55 | 81 | 136 | Synthetic | ||
| 137Cs | 55 | 82 | 137 | Synthetic | ||
| 138Cs | 55 | 83 | 138 | Synthetic | ||
| 139Cs | 55 | 84 | 139 | Synthetic | ||
| 140Cs | 55 | 85 | 140 | Synthetic | ||
| 141Cs | 55 | 86 | 141 | Synthetic | ||
| 142Cs | 55 | 87 | 142 | Synthetic | ||
| 143Cs | 55 | 88 | 143 | Synthetic | ||
| 144Cs | 55 | 89 | 144 | Synthetic | ||
| 145Cs | 55 | 90 | 145 | Synthetic | ||
| 146Cs | 55 | 91 | 146 | Synthetic | ||
| 147Cs | 55 | 92 | 147 | Synthetic | ||
| 148Cs | 55 | 93 | 148 | Synthetic | ||
| 149Cs | 55 | 94 | 149 | Synthetic | ||
| 150Cs | 55 | 95 | 150 | Synthetic | ||
| 151Cs | 55 | 96 | 151 | Synthetic |
Regulatory and Health - Health and Safety Parameters and Guidelines
The United States Department of Transportation (DOT) identifies hazard class of all dangerous elements/goods/commodities either by its class (or division) number or name. The DOT has divided these materials into nine different categories, known as Hazard Classes.
| DOT Numbers | 1407 |
| DOT Hazard Class | 4.3 |
NFPA 704 is a Standard System for the Identification of the Hazards of Materials for Emergency Response. NFPA is a standard maintained by the US based National Fire Protection Association.
The health (blue), flammability (red), and reactivity (yellow) rating all use a numbering scale ranging from 0 to 4. A value of zero means that the element poses no hazard; a rating of four indicates extreme danger.
| Autoignition Point | - |
| Flashpoint | - |
Database Search
List of unique identifiers to search the element in various chemical registry databases
| Database | Identifier number |
|---|---|
| CAS Number - Chemical Abstracts Service (CAS) | CAS7440-46-2 |
| RTECS Number | RTECSFK9225000 |
| CID Number | CID5354618 |
| Gmelin Number | - |
| NSC Number | - |
Compare Cesium with other elements
Compare Cesium with Group 1, Period 6 and Alkali Metal elements of the periodic table.
Compare Cesium with all Group 1 elements
Compare Cesium with all Period 6 elements
Compare Cesium with all Alkali Metal elements
Frequently Asked Questions (FAQ)
Find the answers to the most frequently asked questions about Cesium