thoron

UK: /ˈθɔːrɒn/ US: (thôr′on, thōr′-)

WordReference Random House Unabridged Dictionary of American English © 2026

tho•ron  (thôr′on, thōr′-), n. [Chem.]

1. Chemistry a radioactive isotope of radon, produced by the disintegration of thorium. Symbol: Tn;
   at. wt.: 220;
   at. no.: 86.

• thor(ium) + -on² 1925–30

Collins Concise English Dictionary © HarperCollins Publishers::

thoron / ˈθɔːrɒn/ noun

1. a radioisotope of radon that is a decay product of thorium. Symbol: Tn or ²²⁰Rn; atomic no: 86; half-life: 54.5s

Etymology: 20th Century: from thorium + -on