Nuclei - Result Question 68
69. A nucleus $ _n^{m} X$ emits one $\alpha$-particle and two $\beta$-particles. The resulting nucleus is [2011, 1998]
(a) $ _{n-4}^{m-6} Z$
(b) $ _n^{m-6} Z$
(c) $ _n^{m-4} X$
(d) $ _{n-2}^{m-4} Y$
Show Answer
Answer:
Correct Answer: 69. (c)
Solution:
- (c) When $ _n^{m} X$ emits one $\alpha$-particle then its atomic mass decreases by 4 units and atomic number by 2 . Therefore, the new nucleus becomes $ _{n-2}^{m-4} Y$. But as it emits two $\beta^{-}$particles, its atomic number increases by 2 . Thus the resulting nucleus is $ _n^{m-4} X$.
No radioactive substance emits both $\alpha$ and $\beta$ particles simultaneously. Also, $y$ rays are emitted after the emission of $\alpha$ or beta particle.
