Radon (symbol Rn, atomic number 86) is a radioactive noble gas that seeps from rock and is a leading cause of lung cancer. It is classified as a noble gas and sits in group 18, period 6 of the periodic table.
Overview
Radon is the chemical element with atomic number 86 and the symbol Rn. With a standard atomic weight of [222], it is a noble gas. In the periodic table it occupies group 18 and period 6, and under standard conditions it is normally a gas. Radon is a radioactive noble gas that seeps from rock and is a leading cause of lung cancer.
Atomic structure
An atom of Radon has 86 protons in its nucleus and, when neutral, 86 electrons arranged in the configuration [Xe] 4f14 5d10 6s2 6p6. Radon has no stable isotope; the value [222] refers to the mass number of its most stable or most commonly produced isotope.
Discovery and place in the table
Radon was discovered in 1899 by Ernest Rutherford, Robert B. Owens. It follows Astatine (At) and precedes Francium (Fr) in order of atomic number.
| Atomic number | 86 |
|---|---|
| Symbol | Rn |
| Atomic mass | [222] |
| Category | Noble gas |
| Group | 18 |
| Period | 6 |
| Electron configuration | [Xe] 4f14 5d10 6s2 6p6 |
| Phase at STP | Gas |
| Discovered | 1899 (Ernest Rutherford, Robert B. Owens) |