Radon
noble gasProperties
| Property | Value |
|---|---|
| Atomic Mass | 222 amu |
| Category | noble gas |
| Group | 18 |
| Period | 6 |
| Electron Configuration | [Xe] 4f14 5d10 6s2 6p6 |
| Electronegativity | 2.2 (Pauling) |
| Oxidation States | 2 |
| Melting Point | 202 K (-71.1 °C) |
| Boiling Point | 211.5 K (-61.6 °C) |
| Density | 0.00973 g/cm³ |
| Discovered By | Friedrich Ernst Dorn (1900) |
About Radon
Radon is the heaviest noble gas, dense enough at 9.73 g/L to pool in basements, and the only gaseous element whose every isotope is radioactive. ²²²Rn — the one that matters for public health — is the alpha-emitting daughter of ²²⁶Ra in the uranium-238 decay chain, with a 3.8-day half-life that's just long enough to migrate out of soil and concrete pores into building air. Once inhaled, the short-lived progeny ²¹⁸Po and ²¹⁴Po deposit on bronchial epithelium and dose it with alphas, which is why radon is the second-leading cause of lung cancer after tobacco and the EPA action level of 4 pCi/L exists. Chemistry is sparse but not nothing: RnF₂ and a few cation-like complexes have been characterized, putting radon at the more reactive end of the noble gases. The 1900 discovery by Friedrich Dorn fell out of work showing that thorium and radium 'emanations' were distinct gaseous elements.
Fun Fact
Radon is responsible for the majority of the average person's exposure to ionizing radiation from natural sources — this invisible gas seeps into homes from the ground and is the second leading cause of lung cancer worldwide.
Common Uses
- Continuous radon monitors in homes and schools using alpha-track or ion-chamber detection
- Hydrologic tracer for groundwater discharge into rivers and oceans
- Soil-gas surveys for uranium prospecting and earthquake-precursor research
- Historical implant seeds (Rn-222 'seeds') for brachytherapy until ¹²⁵I and ¹⁹²Ir replaced it
- Reference source for calibrating low-level alpha spectrometers
- Research target for noble-gas chemistry of RnF₂ and cationic Rn(II) species