Alpha decay: mass and atomic number
Uranium-238 (Z = 92) undergoes alpha decay. The product is:
Answer A: explanation for every choice
A
Correct. Alpha decay emits a helium-4 nucleus: mass number drops by 4 and atomic number by 2.
B
Losing four nucleons includes two protons, so the element must change.
C
Neptunium-238 would come from beta-minus decay, which raises Z by 1 and leaves A unchanged.
D
Radium-230 would result from two alpha decays.
TakeawayAlpha: A − 4, Z − 2. Beta-minus: Z + 1. Gamma: no change in A or Z.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp35.