Caesium Atomic Number



Atomic Number of Caesium Atomic Number of Caesium is 55. Chemical symbol for Caesium is Cs. Number of protons in Caesium is 55. Technical data for Cesium. Click any property name to see plots of that property for all the elements.

Cesium Electron Number

  • It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Cs-117 (Caesium, atomic number Z = 55, mass number A = 117).
  • Element Caesium (Cs), Group 1, Atomic Number 55, s-block, Mass 132.905. Sources, facts, uses, scarcity (SRI), podcasts, alchemical symbols, videos and images.

Element Cesium - Cs

Cesium mass numberCaesium Atomic Number

Comprehensive data on the chemical element Cesium is provided on this page; including scores of properties, element names in many languages, most known nuclides of Cesium. Common chemical compounds are also provided for many elements. In addition technical terms are linked to their definitions and the menu contains links to related articles that are a great aid in one's studies.

Cesium Menu

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Overview of Cesium

  • Atomic Number: 55
  • Group: 1
  • Period: 6
  • Series: Alkali Metals

Cesium's Name in Other Languages

  • Latin: Caesium
  • Czech: Cesium
  • Croatian: Cezij
  • French: Césium
  • German: Zäsium - s
  • Italian: Cesio
  • Norwegian: Cesium
  • Portuguese: Césio
  • Russian: Цеэий
  • Spanish: Cesio
  • Swedish: Cesium

Atomic Structure of Cesium

  • Atomic Radius: 3.34Å
  • Atomic Volume: 71.07cm3/mol
  • Covalent Radius: 2.35Å
  • Cross Section (Thermal Neutron Capture)σa/barns: 29
  • Crystal Structure: Cubic body centered
  • Electron Configuration:
    1s2 2s2p6 3s2p6d10 4s2p6d10 5s2p6 6s1
  • Electrons per Energy Level: 2,8,18,18,8,1
    Shell Model
  • Ionic Radius: 1.67Å
  • Filling Orbital: 6s1
  • Number of Electrons (with no charge): 55
  • Number of Neutrons (most common/stable nuclide): 78
  • Number of Protons: 55
  • Oxidation States: 1
  • Valence Electrons: 6s1
    Electron Dot Model

Chemical Properties of Cesium

  • Electrochemical Equivalent: 4.9587g/amp-hr
  • Electron Work Function: 2.14eV
  • Electronegativity: 0.79 (Pauling); 0.86 (Allrod Rochow)
  • Heat of Fusion: 2.092kJ/mol
  • Incompatibilities:
  • Ionization Potential
    • First: 3.894
    • Second: 25.1
  • Valence Electron Potential (-eV): 8.62

Physical Properties of Cesium

  • Atomic Mass Average: 132.9054
  • Boiling Point: 944K 671°C 1240°F
  • Coefficient of lineal thermal expansion/K-1: 97E-6
  • Conductivity
    Electrical: 0.0489 106/cm Ω
    Thermal: 0.359 W/cmK
  • Density: 1.873g/cc @ 300K
  • Description:
    Soft light silvery-white alkali metal.
  • Elastic Modulus:
    • Bulk: 1.6/GPa
    • Rigidity: 0.65/GPa
    • Youngs: 1.7/GPa
  • Enthalpy of Atomization: 78.2 kJ/mole @ 25°C
  • Enthalpy of Fusion: 2.1 kJ/mole
  • Enthalpy of Vaporization: 65.9 kJ/mole
  • Flammablity Class:
  • Freezing Point:see melting point
  • Hardness Scale
    • Brinell: 0.14 MN m-2
    • Mohs: 0.2
  • Heat of Vaporization: 67.74kJ/mol
  • Melting Point: 301.7K 28.55°C 83.39°F
  • Molar Volume: 70.73 cm3/mole
  • Physical State (at 20°C & 1atm): Solid
  • Specific Heat: 0.24J/gK
  • Vapor Pressure 2.5kPa

Regulatory / Health

  • CAS Number
    • 7440-46-2
  • RTECS: FK9225000
  • OSHAPermissible Exposure Limit (PEL)
    • No limits set by OSHA
  • OSHA PEL Vacated 1989
    • No limits set by OSHA
  • NIOSHRecommended Exposure Limit (REL)
    • No limits set by NIOSH
  • Levels In Humans:
    Note: this data represents naturally occuring levels of elements in the typical human, it DOES NOT represent recommended daily allowances.
    • Blood/mg dm-3: 0.0038
    • Bone/p.p.m: 0.013-0.052
    • Liver/p.p.m: 0.04-0.05
    • Muscle/p.p.m: 0.07-1.6
    • Daily Dietary Intake: 0.004-0.03 mg
    • Total Mass In Avg. 70kg human: 6 mg

Who / Where / When / How

  • Discoverer: Gustov R. Kirchoff, Robert Bunsen
  • Discovery Location: Heidelberg Germany
  • Discovery Year: 1860
  • Name Origin:
    Latin: caesius (sky blue); its salts turn flames blue.
  • Abundance of Cesium:
    • Earth's Crust/p.p.m.: 3
    • Seawater/p.p.m.: 0.0003
    • Atmosphere/p.p.m.: N/A
    • Sun (Relative to H=1E12): 80
  • Sources of Cesium:
    Found in pollucite [(Cs4Al4Si9O26).H2O] and as trace in lepidolite. World production is around 20 tons per year. Primary mining areas are in Bernic Lake (Manitoba, Canada), Bikita (Zimbabwe) and South-West Africa.
  • Uses of Cesium:
    Used as a 'getter' to remove air traces in vacuum tubes. Since it ionizes readily, it is used as an ion rocket motor propellant. Also used in photoelectric cells, atomic clocks, infared lamps.
  • Additional Notes:
    Cesium can have very serious effects on the body if taken in excess.

Cesium Menu

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References

A list of reference sources used to compile the data provided on our periodic table of elements can be found on the main periodic table page.

Related Resources

  • Anatomy of the Atom
    Answers many questions regarding the structure of atoms.
  • Molarity, Molality and Normality
    Introduces stoichiometry and explains the differences between molarity, molality and normality.
  • Molar Mass Calculations and Javascript Calculator
    Molar mass calculations are explained and there is a JavaScript calculator to aid calculations.
  • Chemical Database
    This database focuses on the most common chemical compounds used in the home and industry.

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Kenneth Barbalace. Periodic Table of Elements - Cesium - Cs. EnvironmentalChemistry.com. 1995 - 2021. Accessed on-line: 4/25/2021
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