The radioisotope ^ 235 92 U decays by emitting two alpha particles, three beta particles and a gamma ray. What…

Analyze the question: U-235 (mass number 235, atomic number 92) emits 2 alpha particles, 3 beta particles and 1 gamma ray. We need the mass number and atomic number of the daughter nucleus.

Concept:

• Alpha particle (⁴₂He): mass number drops by 4, atomic number drops by 2.
• Beta particle (⁰₋₁e): mass number unchanged, atomic number increases by 1.
• Gamma ray: no change in mass or atomic number.

Solution:

Mass number: 235 − (2 × 4) = 235 − 8 = 227

Atomic number: 92 − (2 × 2) + (3 × 1) = 92 − 4 + 3 = 91

So the resulting nucleus is ²²⁷₉₁Pa (protactinium-227).

Check against options:

• A. 215 and 88: wrong
• B. 91 and 227: the numbers are right but in the wrong order (the question asks for mass and atomic number, in that order)
• C. 227 and 91: mass number 227, atomic number 91, which matches
• D. 92 and 238: wrong

Tip: For decay questions, keep two separate tallies. Mass number only changes with alpha (−4 each). Atomic number changes with alpha (−2 each) and beta (+1 each). Gamma changes nothing. Also read the option order carefully: option B has the right numbers swapped, which is a common JAMB trap.