Radon (Rn)
Element 86 · Noble gas · Gas at 25 °C · Group 18, Period 6
Radon is a radioactive noble gas produced by the decay of uranium in rock; it can seep into basements, where it is a recognized health hazard worth testing for.
On the periodic table, radon sits in group 18 — the noble gases — in period 6. It is one of 7 elements classified as a noble gas, and at room temperature (25 °C) it is a gas — one of 11 elements that are gases at room temperature.
The noble gases of group 18 have completely filled outer electron shells, so they have almost no urge to react with anything. All the naturally occurring members are colorless, odorless, monatomic gases at room temperature. Their aloofness is useful in its own right — inert atmospheres, lighting, and cryogenics all rely on it.
Properties of radon
| Atomic number (Z) | 86 |
|---|---|
| Symbol | Rn |
| Atomic mass | (222) (mass number of the most stable isotope; this element has no standard atomic weight) |
| Category | Noble gas |
| Group | 18 |
| Period | 6 |
| Block | p-block |
| Metal / nonmetal | Nonmetal |
| State at 25 °C | Gas |
| Electron configuration | [Xe] 4f14 5d10 6s2 6p6 |
| Electronegativity (Pauling) | 2.2 |
| Melting point | -71 °C (202.15 K / -95.8 °F) |
| Boiling point | -61.7 °C (211.45 K / -79.06 °F) |
| Density | 0.00973 g/cm³ |
Position in the periodic table
Radon shares group 18 — the noble gases with Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Oganesson (Og). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.
Physical properties
Radon melts at -71 °C (202.15 K / -95.8 °F) and boils at -61.7 °C (211.45 K / -79.06 °F), giving it a liquid range of about 9.3 °C at standard pressure.
As a gas at standard conditions, its density is 0.00973 g/cm³ — measured at STP like the other gaseous elements here.
Data notes
The atomic mass is shown in parentheses because this element has no standard atomic weight; the number given is the mass number of its most stable known isotope.
See also: the interactive periodic table, how to read the periodic table, the element families tour.