Multiple choice After how many alpha & beta decays Th-234 will produce Ra-220? 2 alpha + 3 beta 7 alpha + 4 beta 5 alpha + 4 beta 4 alpha + 3 beta Reveal answer Fill a bubble to check yourself A Correct answer Explanation The uranium decay-series contains several radioactive isotopes.U-238 decays by alpha emission into thorium Th-234. Th-234 decays by 2 alpha & 3 beta emission changes into Ra-220.