Radon is the only naturally occurring radioactive noble gas. This element is produced by the decay of uranium and other radioactive metals. Being a gas, radon escapes from minerals, such as uraninite, into the air. Radon is highly radioactive and breathing it can cause illnesses, such as lung cancer. In most places, radon concentrations in the air are very low. However, its levels increase around volcanic springs and in muds, where it bubbles with other hot gases. Radon is also present in water in geothermal power plants, which use thermal energy from deep volcanic rocks to produce electricity. Radon is also more common in areas rich in granite rocks. In these places, people often monitor radon levels in their homes.

Summary of properties (Rn)

Atomic weight[222]
Discoverer (year)Dorn, Friedrich Ernst (1900)
Natural formgas
Electron configuration[Xe] 414 5d10 6s2 6p6
Melting point (ºC)-71
Boiling point (ºC)-62
Abundance in earth's crust (ppm)<0.001
Isotope (abundance)
Density g/cm39.73
Van der Waals radius (pm)220
Covalent radius (pm)146
Electronegativity (Pauling)
Vaporization enthalpy (kJ/mol)18.10
Enthalpy of fusion (kJ/mol)2.89
Specific heat capacity (J/g·K) at 25ºC and 1 atm0.09
Thermal conductivity (W/cm·K) at 25ºC and 1 atm<0.001
Oxidation state0
Electron affinity (eV)unstable ion
1st Ionization potential (eV)10.7485

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