Modern Physics 3 Question 43
42. A uranium nucleus (atomic number 92 , mass number 238) emits an alpha particle and the resulting nucleus emits $\beta$-particle. What are the atomic number and mass number of the final nucleus?
$(1982,2 M)$
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Answer:
Correct Answer: 42. (a) 91 (b) 234
Solution:
- ${ } _{92} U^{238} \stackrel{\alpha \text {-decay }}{\rightarrow}{ } _{90} X^{234} \quad \beta$ - decay $\rightarrow{ } _{91} Y^{234}$
During an $\alpha$-decay atomic number decreases by 2 and mass number by 4 . During a $\beta$-decay, atomic number increases by 1 while mass number remains unchanged.
