If a nucleus of Th absorbs a neutron and the resulting nucleus undergoes two successive beta decays (emitting electrons), what nucleus results?

Question

If a nucleus of  Th absorbs a neutron and the resulting nucleus undergoes two successive beta decays (emitting electrons), what nucleus results?

Quizplus · Accepted Answer

The given nucleus 11ea8004_e37f_cf31_846e_43429a9ec280_TB4071_11 Th has a mass number of 238 and atomic number of 90. 
Absorbing a neutron would result in a new nucleus with a mass number of 239 and atomic number of 90+1=91, which is protactinium-239. 
Two successive beta decays result in the conversion of two neutrons into two protons, resulting in an atomic number of 93. 
The only option with atomic number 93 is uranium-233 (choice D).

If a Nucleus of Th Absorbs a Neutron and the Resulting