A radioisotope decays, producing an alpha particle and Th-234. The original radioisotope must have been an atom of ________.

Question

Quizplus · Accepted Answer

When a radioisotope decays by emitting an alpha particle (which consists of 2 protons and 2 neutrons), the atomic number decreases by 2 and the mass number decreases by 4. Th-234 (Thorium-234) has an atomic number of 90 and a mass number of 234. Therefore, the original radioisotope must have had an atomic number of 92 (90 + 2) and a mass number of 238 (234 + 4), which corresponds to Uranium (U).

A Radioisotope Decays, Producing an Alpha Particle and Th-234