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. [
PJC]