|—the chemical symbol for|
|1.||(in Canada) Registered Nurse|
|3.||Niger (international car registration)|
|[(sense 3) From R(epublic of) N(iger)]|
The symbol for the element radon.
RN or R.N.
The symbol for radon.
|radon (rā'dŏn) Pronunciation Key
A colorless, odorless, radioactive element in the noble gas group. It is produced by the radioactive decay of radium and occurs in minute amounts in soil, rocks, and the air near the ground. Radon is used as a source of radiation for the treatment of cancer and other diseases. Its most stable isotope is Rn 222 with a half-life of 3.82 days. Atomic number 86; melting point -71°C; boiling point -61.8°C; specific gravity (solid) 4. See Periodic Table.