The radioactive nuclide $^{232}_{90}Th$ decays by one $ ext{α}$ emission followed by two $ ext{β}^-$ emissions - AQA - A-Level Physics - Question 10 - 2020 - Paper 1
Question 10
The radioactive nuclide $^{232}_{90}Th$ decays by one $ ext{α}$ emission followed by two $ ext{β}^-$ emissions.
Which nuclide is formed as a result of these decays?... show full transcript
Worked Solution & Example Answer:The radioactive nuclide $^{232}_{90}Th$ decays by one $ ext{α}$ emission followed by two $ ext{β}^-$ emissions - AQA - A-Level Physics - Question 10 - 2020 - Paper 1
Step 1
Calculate the nuclide after one α emission
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Answer
In an α emission, the nuclide loses 2 protons and 4 nucleons. Therefore:
Initial nuclide: 90232Th
After 1 extα emission:
90−2232−4Th=88228Ra
Step 2
Calculate the nuclide after one β- emission
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Answer
In a β- emission, a neutron is converted into a proton, resulting in an increase in the atomic number by 1 but the mass number remains the same.
For 88228Ra, after 1 extβ− emission:
ightarrow ^{228}_{89}Ac$$
Step 3
Calculate the nuclide after second β- emission
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Answer
Again performing a second β- emission on 89228Ac:
After 2 extβ− emissions, it becomes:
ightarrow ^{228}_{90}Th$$
Step 4
Final Answer
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Answer
The final nuclide formed after these decays is 90228Th. This corresponds to option C.
