D defs.my
Entry 1 sense Webster, 1913

radiothorium

/(rā`dĭ*ŏ*thôr"ē*ŭm)/ · ra·di·o·tho·ri·um · IPA
01 n. an earlier name for the thorium isotope thorium-228, given by its discoverer Otto Hahn. It is a radioactive substance formed as one of ser…
  1. 1.
    an earlier name for the thorium isotope thorium-228, given by its discoverer Otto Hahn. It is a radioactive substance formed as one of series of products in the chain of radioactive decay of thorium. Its immediate predecessor in the chain is Actinium-228, and it decays by alpha emission to radium-224 with a half-life of 1.91 years. The name radiothorium was given prior to the full understanding of the nature of isotopes of elements.(Chem.) Also: thorium-228