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Name: radon Symbol: Rn Named after "the element radium" (radon was called niton at first, from the Latin word "nitens" meaning "shining") Block in periodic table: p-block Standard state: gas Colour: colourless CAS: 10043-92-2 Description At ordinary temperatures radon is a colourless gas. When cooled below the freezing point, radon exhibits a brilliant phosphorescence which becomes yellow as the temperature is lowered and orange-red at the temperature of liquid air. The main hazard is from inhalation of the element and its decay products which are collected on dust in the air. Recently, radon buildup in homes from the surrounding soil and rocks has become a safety issue and some areas around the world test homes for radon gas. It is the heaviest known gas. Radon is present in some spring waters. Historical Radon was discovered in 1900 by Friedrich Ernst Dorn, who called it niton. It is essentially inert. It was called niton but has been called radon since 1923. Discoveror: Friedrich Ernst Dorn Discovered at: Germany Discovery date: 1900 ******************************************************************************** Atomic number: 86 Standard atomic weight: 222.02 Symbol: Rn Group number: 18 Electronic configuration: [Xe].4f14.5d10.6s2.6p6 Physical state Standard state: gas Colour: colourless Density/kg m-3: n.a. [solid]; 4400 [liquid at boiling point]; 9.73 [gas, 273 K] Molar volume/cm3: 50.5 [211 K] Radii /pm Uncharged Atomic: n.a. Covalent: n.a. van der Waals: n.a. Metallic: n.a. Pauling: n.a. univalent ionic: n.a. Valence shell orbital radius maxima (Rmax) orbital : pm s: 99.7 p: 113.2 d: 49.2 f: 16.8 atomic units s: 1.88420 p: 2.13933 d: 0.930166 f: 0.317813 Electronegativities All values are quoted on the Pauling scale apart from absolute values which are given in eV. Pauling: n.a. Sanderson: n.a. Allred Rochow: 2.06 Absolute (/eV): 5.1 Effective nuclear charges Slater: 8.25 Clementi: 16.08 Froese-Fischer: 20.84 Temperatures /K melting point: 202 boiling point: 211.4 m.p. hydride: n.a. b.p. hydride: n.a. b.p. fluoride: n.a. Enthalpies /kJ mol-1 fusion: 2.7 (est.) vaporisation: 18.1 Single bond enthalpies Rn-F: n.a. Rn-F: n.a. Rn-Br: n.a. Rn-I: n.a. Rn-Rn: n.a. Ionization enthalpies 1st: 1037 2nd: 1930 3rd: 2890 4th: 4250 5th: 5310 Isotope data for naturally occurring isotopes % natural abundance: nil 
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