In the Four Radioactive Series,the Nuclei Decay by Either Emitting

Multiple Choice

In the four radioactive series,the nuclei decay by either emitting alpha particles or beta particles until they reach the stable end product.Each decay,therefore,results in a mass number change of either 4 (for alpha decay) or 0 (for beta decay) .The radium isotope ²²⁶Ra is in one of these series.What is the starting isotope in the series containing ²²⁶Ra?

A) ²³⁸U
B) ²³⁵U
C) ²³²Th
D) ²³⁷Np