Radium, 88 Ra General properties Pronunciation Template:Infobox element/pronunciation Appearance silvery white metallic Standard atomic weight (A r, standard ) Template:Infobox element/standard atomic weight Mass number Template:Infobox element/symbol-to-most-stable-isotope (most stable isotope)Radium in the periodic table Template:Infobox element/periodic table Atomic number (Z ) 88 Group Template:Infobox element/group Period period 7 Block s-block Element category Template:Infobox element/category format Electron configuration [Rn ] 7s2 Electrons per shell
2, 8, 18, 32, 18, 8, 2 Physical properties Phase at STP solid Melting point 973 K (700 °C, 1292 °F) (disputed) Boiling point 2010 K (1737 °C, 3159 °F) Density (near r.t. ) 5.5 g/cm3 Heat of fusion 8.5 kJ/mol [[Enthalpy of vaporization|Heat of Template:Engvar ]] 113 kJ/mol [[Vapor pressure|Template:Engvar pressure ]] Atomic properties Oxidation states Template:Infobox element/symbol-to-oxidation-state Electronegativity Pauling scale: 0.9 [[Ionization energy|Template:Engvar energies]] 1st: 509.3 kJ/mol 2nd: 979.0 kJ/mol Covalent radius 221±2 pm Van der Waals radius 283 pm Template:Infobox element/spectral lines Other properties Crystal structure Template:Infobox element/crystal structure Thermal conductivity 18.6 W/(m·K) Electrical resistivity 1 µΩ·m (at 20 °C) Magnetic ordering nonmagnetic CAS Number 7440-14-4 History Discovery Pierre and Marie Curie (1898) First isolation Marie Curie (1910) Main isotopes of radium Template:Infobox element/isotopes table | references
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