Identifying positron emission
Carbon-11 (Z = 6) decays to boron-11 (Z = 5). Which decay mode is this?
Answer D: explanation for every choice
A
Beta-minus decay increases Z by 1.
B
Alpha decay reduces A by 4 and Z by 2.
C
Gamma emission doesn't change A or Z.
D
Correct. A proton becomes a neutron, emitting a positron, so Z drops by 1 and A stays the same. Electron capture gives the same result.
Takeawayβ⁺ or electron capture: Z − 1, same A. β⁻: Z + 1, same A.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp132.