Cesium (Cs) Elemental Symbol

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Césium Cesium Cesio Césio Cesio Cesium

Cesium(Cs) and molecular weight, atomic number and elemental symbolCesium (or Caesium ) is a Block S, Group 1, Period 6 element. The number of electrons in each of Cesium's shells is 2, 8, 18, 18, 8, 1 and its electronic configuration is [Xe] 6s1. The cesium atom has a radius of 265.5.pm and its Van der Waals radius is 200.pm. In its elemental form, CAS 7440-46-2, cesium has a silvery gold appearance. Cesium is a member of the alkali group of metals. It is one of three metals that occur as a liquid at room Cesium Bohr Model temperature - the others are mercury and gallium. Elemental CesiumCesium's main commercial source is pollucite ore; however, it is also found in beryl, avogadrite, pezzottaite, and londonite. Cesium was first discovered by Robert Bunsen and Gustav Kirchhoff in 1860. Cesium is named for the vibrant blue lines in its spectrum. The word Cesium originates from the Latin word caesius, meaning "sky blue". Cesium information, including technical data, safety data, high purity properties, research, applications and other useful facts are discussed below. Scientific facts such as the atomic structure, ionization energy, abundance on earth, conductivity and thermal properties are also included.

Cesium is used as an oxygen "getter" in vacuum and electronic tubes and as a component of photoelectric cells. Atomic clocks use the microwave spectral line emitted by Cesium Isotope 133 for reference. Radioactive Cesium 137 is an artificial isotope that is used for cancer radiotherapy. High Purity (99.999%) Cesium Oxide (Cs2O) PowderLaboratories use various cesium compounds for their ability to hydrogenate organic compounds. Cesium is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity). Nanoparticles and nanopowders provide ultra-high surface area which nanotechnology research and recent experiments demonstrate function to create new and unique properties and benefits. Oxides are available in forms including powders and dense pellets for such uses as optical coating and thin film applications. Oxides tend to be insoluble. Fluorides are another insoluble form for uses in which oxygen is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Cesium is available in soluble forms including chlorides, nitrates and acetates. These compounds are also manufactured as solutions at specified stoichiometries.

Cesium compounds are slightly toxic. Safety data for Cesium and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab below.

  • Properties
  • Safety Data
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  • Research
  • Isotopes
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Cesium Properties

Symbol: Cs Melting Point: 301.59 K, 28.44 °C, 83.19 °F
Atomic Number: 55 Boiling Point: 944 K, 671 °C, 1240 °F
Atomic Weight: 132.9054519 Density: 1.93 g·cm−3
Element Category: alkali metal Liquid Density @ Melting Point: 1.843 g·cm−3
Group, Period, Block: 1 , 6, s Specific Heat: 0.24J/gK
    Heat of Vaporization 66.5 kJ mol-1
CHEMICAL STRUCTURE Heat of Fusion 2.09 kJ mol-1
Electrons: 55 Thermal Conductivity: 35.9 W·m−1·K−1
Protons: 55 Thermal Expansion: (25 °C) 97 µm·m−1·K−1
Neutrons: 78 Electrical Resistivity: (20 °C) 205 nΩ·m
Electron Configuration: [Xe 6s1 2, 8, 18, 18, 8, 1 Electronegativity: 0.79 (Pauling scale)
Atomic Radius: 265 pm Tensile Strength: N/A
Covalent Radius: 244±11 pm Molar Heat Capacity: 32.210 J·mol−1·K−1
Van der Waals radius: 343 pm Young's Modulus: 1.7 GPa
Oxidation States: 1 (strongly basic oxide) Shear Modulus: N/A
Phase: Solid Bulk Modulus: 1.6 GPa
Crystal Structure: body-centered cubic Poisson Ratio: N/A
Magnetic Ordering: paramagnetic Mohs Hardness: 0.2
1st Ionization Energy: 375.71 kJ mol-1 Vickers Hardness: N/A
2nd Ionization Energy: 2234.37 kJ mol-1 Brinell Hardness: 0.14 MPa
3rd Ionization Energy: 3rd: 3400 kJ·mol−1 Speed of Sound: N/A
CAS Number: 7440-46-2 Abundance in typical human body, by weight: 20 ppb
ChemSpider ID: 4510778 Abundance in typical human body, by atom: 1 ppb
PubChem CID: 5354618 Abundance in universe, by weight: 0.8 ppb
MDL Number: MFCD00134037 Abundance in universe, by atom: 0.1 ppb
EC Number: 231-155-4 Discovered By: Robert Bunsen and Gustav Kirchhoff
Beilstein Number: N/A Discovery Date: 1860
SMILES Identifier: [Cs]  
InChI Identifier: InChI=1S/Cs Other Names: Caesium

Health, Safety & Transportation Information for Cesium

Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H260-H314
Hazard Codes F,C
Risk Codes 11-14/15-34
Safety Precautions 8-16-26-36/37/39-43-45
RTECS Number FK9225000
Transport Information UN 1415 4.3/PG 1
WGK Germany 3
Globally Harmonized System of
Classification and Labelling (GHS)
Corrosion-Corrosive to metals Flame-Flammables  

Recent Research & Development for Cesium

  • Pankaj Kandwal, Prasanta Kumar Mohapatra, A highly efficient solvent system containing chlorinated cobalt dicarbollide in NPOE—Dodecane mixture for effective transport of radio-cesium from acidic wastes, Journal of Membrane Science, Volume 469, 1 November 2014
  • J.N. Sharma, Amar Kumar, Vikas Kumar, S. Pahan, C. Janardanan, V. Tessi, P.K. Wattal, Process development for separation of cesium from acidic nuclear waste solution using 1,3-dioctyloxycalix[4]arene-crown-6 + isodecyl alcohol/n-dodecane solvent, Separation and Purification Technology, Volume 135, 15 October 2014
  • Andrey Vendilo, Konstantin Popov, Marja Lajunen, Vyacheslav Chistov, Dmitry Djigailo, Hannu Rönkkömäki, Viktor Privalov, Igor Pletnev, A cesium-133 nuclear magnetic resonance study of the cesium cation сomplexation by macrocyclic polyethers in hydrophobic RITLs, Polyhedron, Volume 81, 15 October 2014
  • Sarah N. Spisak, Alexander V. Zabula, Alexander S. Filatov, Marina A. Petrukhina, Self-assembly of charged corannulene with cesium ions: Always in the bowl, Journal of Organometallic Chemistry, Available online 2 September 2014
  • Kitheri Joseph, K.V. Govindan Kutty, M.C. Goswami, P.R. Vasudeva Rao, Viscosity and crystallization mechanism of cesium loaded iron phosphate glasses, Thermochimica Acta, Volume 587, 10 July 2014
  • Sathasivam Pratheep Kumar, Buvaneswari Gopal, Synthesis and leachability study of a new cesium immobilized langbeinite phosphate: KCsFeZrP3O12, Journal of Alloys and Compounds, Volume 615, 5 December 2014
  • Hang Long, Pingxiao Wu, Lin Yang, Zhujian Huang, Nengwu Zhu, Zhixian Hu, Efficient removal of cesium from aqueous solution with vermiculite of enhanced adsorption property through surface modification by ethylamine, Journal of Colloid and Interface Science, Volume 428, 15 August 2014
  • Alfred K. Hill, Laura Torrente-Murciano, In-situ H2 production via low temperature decomposition of ammonia: Insights into the role of cesium as a promoter, International Journal of Hydrogen Energy, Volume 39, Issue 15, 15 May 2014
  • Yan-Hong Deng, Yan-Qing Li, Qing-Dong Ou, Qian-Kun Wang, Fu-Zhou Sun, Xiang-Yu Chen, Jian-Xin Tang, The doping effect of cesium-based compounds on carrier transport and operational stability in organic light-emitting diodes, Organic Electronics, Volume 15, Issue 6, June 2014
  • N. Osada, K. Ishii, S. Matsuyama, H. Sugai, K. Kusano, Y. Nozawa, S. Yamauchi, M. Karahashi, S. Oshikawa, K. Kikuchi, S. Koshio, K. Watanabe, S. Itoh, Y. Suzuki, A. Terakawa, Y. Kikuchi, F. Fujishiro, A. Ishizaki, H. Arai, Remediation of plants contaminated with cesium by aqueous cleaning, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 318, Part A, 1 January 2014

Cesium Isotopes

Caesium (Cs) has 40 known isotopes with atomic masses ranging from 112 to 151. 133Cs is the only stable isotope.

Nuclide Symbol Isotopic Mass Half-Life Nuclear Spin
133Cs 132.905451933 Stable 7/2+