Radon (Rn)
Noble gas · p-block · period 6 · group 18
Colourless, odourless, radioactive gas; glows yellow to orange-red when frozen solid.
Radon (symbol Rn) is chemical element number 86, a noble gas in group 18, period 6 of the periodic table. Its standard atomic weight is (222) and its electron configuration is [Xe] 4f14 5d10 6s2 6p6. At room temperature it is a gas, and it is radioactive. The heaviest and only radioactive noble gas.
Properties
| Atomic number | 86 |
|---|---|
| Atomic mass | (222) |
| Category | Noble gas |
| Block | p-block |
| Group · Period | 18 · 6 |
| Electron configuration | [Xe] 4f14 5d10 6s2 6p6 |
| Electrons per shell | 2, 8, 18, 32, 18, 8 |
| State at 25 °C | gas |
| Melting point | 202 K |
| Boiling point | 211.5 K |
| Density | 9.73 g/L |
| Electronegativity (Pauling) | 2.2 |
| Radioactive | Yes — no stable isotope |
| Origin | decay |
| Discovered | 1899 · Ernest Rutherford & Robert Owens |
Key facts about Radon
- The heaviest and only radioactive noble gas.
- Seeps out of uranium-bearing rock and soil and collects in poorly ventilated basements.
- The second leading cause of lung cancer after smoking.
- Made continuously by the decay of radium, hence the name.
What Radon is used for
Historically used in cancer radiotherapy; now mainly monitored as a health hazard and studied for earthquake prediction.
Where it sits in the periodic table
Radon is in group 18, period 6, of the p-block. Its electron configuration [Xe] 4f14 5d10 6s2 6p6 means its outermost shell holds 8 electrons, which is what places it here and explains much of its chemistry. See Radon on the interactive table →
Radon — frequently asked questions
What is Radon used for?
Historically used in cancer radiotherapy; now mainly monitored as a health hazard and studied for earthquake prediction.
Is Radon radioactive?
Yes. Radon has no stable isotope, so every form of it is radioactive.
What is the electron configuration of Radon?
Radon has the electron configuration [Xe] 4f14 5d10 6s2 6p6, which is 2, 8, 18, 32, 18, 8 electrons per shell.
What group and period is Radon in?
Radon is in group 18, period 6, in the p-block. Its outer shell holds 8 electrons.
Who discovered Radon?
Radon was discovered in 1899 by Ernest Rutherford & Robert Owens.