## Emissions

Radon spectrum is 400 nm - 700 nm. Credit: McZusatz.{{free media}}

## Gases

Radon is, under standard conditions, gaseous and easily inhaled, and therefore a health hazard.

Radon is "one of the noble gases."[1]

The molecules Rn
2
and RnXe were found to be significantly stabilized by spin-orbit coupling.[2]

Radon is a colorless, odorless, and tasteless[3] gas and therefore is not detectable by human senses alone. At standard temperature and pressure, it forms a monatomic gas with a density of 9.73 kg/m3, about 8 times the density of the Earth's atmosphere at sea level, 1.217 kg/m3.[4] It is one of the densest gases at room temperature and is the densest of the noble gases.

## Liquids

Although colorless at standard temperature and pressure, when cooled below its freezing point of 202 K (−71 °C; −96 °F), it emits a brilliant radioluminescence that turns from yellow to orange-red as the temperature lowers.[5] Upon condensation, it glows because of the intense radiation it produces.[6] It is sparingly soluble in water, but more soluble than lighter noble gases. It is appreciably more soluble in organic liquids than in water. Its solubility equation is as follows,[7][8][9]

${\displaystyle \chi =\exp(B/T-A)}$ ,

where ${\displaystyle \chi }$  is the molar fraction of Radon, ${\displaystyle T}$  is the absolute temperature, and ${\displaystyle A}$  and ${\displaystyle B}$  are solvent constants.

## Alloys

Radon carbonyl (RnCO) has been predicted to be stable and to have a linear molecular geometry.[10]