O-LevelPhysicsNuclear Physics5054/21 · Oct/Nov 2024 · Q88 Marks
The nuclide notation for the radioactive isotope hydrogen-3 is ³₁H.
- (a)Explain why hydrogen-3 cannot decay by the emission of alpha particles.[1]
- (b)Hydrogen-3 decays by the emission of beta particles to an isotope of a different element. This element is represented in the equation by Q.
- (b)(i)Complete the nuclide equation for the decay of hydrogen-3. ³₁H → ...........₀⁻₁β + ...........Q [3][3]
- (b)(ii)State the name of the element represented by Q.[1]
- (c)The half-life of hydrogen-3 is 12 years.
- (c)(i)Define 'half-life'.[2]
- (c)(ii)A sample of hydrogen-3 is placed on a laboratory bench next to a Geiger-Müller tube and counter. The count rate is recorded at the same time on four successive days. Table 8.1 shows the count rates obtained. Table 8.1 day 1 2 3 4 count rate counts/s 98 89 93 85 State why the count rate decreases and increases.[1]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.
- [B1] (a nucleus of hydrogen–3) contains only 3 nucleons or only 1 proton
- [B1] ⁰₋₁β
- [B1] ³Q
- [B1] ²
- [B1] helium
- [C1] time taken for something to halve
- [A1] time taken for number of atoms / (corrected) count rate to halve
- [B1] (due to) spontaneous / random nature of decay
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