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In a radioactive decay chain, the initial nucleus is Th 232 90 . At the end there are 6 α -particles and 4 β -particles which are emitted. If the end nucleus is X A Z , A and Z are given by :

1. A = 208 ; Z = 80
2. A = 208 ; Z = 82
3. A = 200 ; Z = 81
4. A = 202 ; Z = 80

Correct answer: A = 208 ; Z = 82

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