Technical data for Cesium

Overview Name Cesium Symbol Cs Atomic Number 55 Atomic Weight 132.90545196 Density 1.879 g/cm3 Melting Point 28.44 °C Boiling Point 671 °C Thermal properties Phase Solid Melting Point 28.44 °C Boiling Point 671 °C Absolute Melting Point 301.59 K Absolute Boiling Point 944 K Critical Pressure 9.4 MPa (92.77 Atm) Critical Temperature 1938 K Heat of Fusion 2.09 kJ/mol Heat of Vaporization 64 kJ/mol Specific Heat 242 J/(kg K)[note] Adiabatic Index N/A Neel Point N/A Thermal Conductivity 36 W/(m K) Thermal Expansion N/A Bulk physical properties Density 1.879 g/cm3 Density (Liquid) 1.843 g/cm3 Molar Volume 0.000070732 Brinell Hardness 0.14 MPa Mohs Hardness 0.2 Vickers Hardness N/A Bulk Modulus 1.6 GPa Shear Modulus N/A Young Modulus 1.7 GPa Poisson Ratio N/A Refractive Index N/A Speed of Sound N/A Thermal Conductivity 36 W/(m K) Thermal Expansion N/A Reactivity Valence 1 Electronegativity 0.79 ElectronAffinity 45.5 kJ/mol Ionization Energies 375.7, 2234.3, 3400 kJ/mol Health and Safety DOT Hazard Class 4.3 DOT Numbers 1407 RTECS Number RTECSFK9225000 NFPA Label

Classifications Alternate Names Caesium Names of Allotropes None Block s Group 1 Period 6 Series Alkali Metal Electron Configuration [Xe]6s1 Color Silver Discovery 1860 in Germany Gas phase N/A CAS Number CAS7440-46-2 CID Number CID5354618 RTECS Number RTECSFK9225000 Electrical properties Electrical Type Conductor Electrical Conductivity 5×106 S/m Resistivity 2×10-7 m Ω Superconducting Point N/A Magnetic properties Magnetic Type Paramagnetic Curie Point N/A Mass Magnetic Susceptibility 2.8×10-9 m3/Kg Molar Magnetic Susceptibility 3.72×10-10 m3/mol Volume Magnetic Susceptibility 5.26×10-6 Abundances % in Universe 8×10-8% % in Sun 8×10-7% % in Meteorites 0.000014% % in Earth's Crust 0.00019% % in Oceans 5×10-8% % in Humans 2×10-6% Atomic dimensions and structure Atomic Radius 298 pm Covalent Radius 244 pm Van der Waals Radius N/A Crystal Structure Body-centered Cubic Lattice Angles π/2, π/2, π/2 Lattice Constants 614.1, 614.1, 614.1 pm Space Group Name Im_ 3m Space Group Number 229 Nuclear Properties Half-Life Stable Lifetime Stable Decay Mode N/A Quantum Numbers 2S1/2 Neutron Cross Section 29 Neutron Mass Absorption 0.0077 Known Isotopes 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 Stable Isotopes 133Cs Isotopic Abundances 133Cs 100%