Cambridge International AS & A Level · 11 · structured
Construct complete radioactive decay equations
Balance alpha, beta-minus and beta-plus nuclide equations · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- demanding
- Marks
- 9
- Topics
- 1
- Answer
- Complete
Write complete nuclide equations for (a) alpha decay of ²¹⁰₈₄Po to Pb, (b) beta-minus decay of ³²₁₅P to S, and (c) beta-plus decay of ¹¹₆C to B. Include required (anti)neutrinos and show A and charge conservation in each case.
- (a)
Alpha decay of ²¹⁰₈₄Po to Pb.
3 marks - (b)
Beta-minus decay of ³²₁₅P to S.
3 marks - (c)
Beta-plus decay of ¹¹₆C to B.
3 marks
Ready to self-mark?Reveal the detailed answer guide
(a)
Alpha decay of ²¹⁰₈₄Po to Pb.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
²¹⁰₈₄Po → ²⁰⁶₈₂Pb + ⁴₂He; A210=206+4, Z84=82+2.
(b)
Beta-minus decay of ³²₁₅P to S.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
³²₁₅P → ³²₁₆S + ⁰₋₁e + ⁰₀ν̄ₑ; A32=32, Z15=16−1.
(c)
Beta-plus decay of ¹¹₆C to B.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
¹¹₆C → ¹¹₅B + ⁰₊₁e + ⁰₀νₑ; A11=11, Z6=5+1.
Complete marking guidance
Use these worked steps alongside the part-by-part answers. They explain the method and mark allocation; they do not add extra marks.
- Alpha decay: ²¹⁰₈₄Po → ²⁰⁶₈₂Pb + ⁴₂He. Nucleon numbers give 210 = 206 + 4, and charges give 84 = 82 + 2.
- Beta-minus decay: ³²₁₅P → ³²₁₆S + ⁰₋₁e + an electron antineutrino. The totals are 32 = 32 + 0 + 0 and 15 = 16 − 1 + 0.
- Beta-plus decay: ¹¹₆C → ¹¹₅B + ⁰₊₁e + an electron neutrino. The totals are 11 = 11 + 0 + 0 and 6 = 5 + 1 + 0.
- Require complete A/Z notation, daughter symbols, and proper beta signs.
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