radioactinium

[ rey-dee-oh-ak-tin-ee-uh m ]

/ ˌreɪ di oʊ ækˈtɪn i əm /

noun Chemistry.

the radioactive isotope of thorium having a mass number 227 and a half-life of 18.8 days. Symbol: RdAc, Th 227

Nearby words

radio window, radio-, radio-collar, radio-controlled, radioacoustics, radioactinium, radioactivate, radioactive, radioactive constant, radioactive dating, radioactive decay

Origin of radioactinium

First recorded in 1905–10; radio- + actinium

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019