Question

In the nuclear reaction, ${}_{72}{X}^{180}\stackrel{{}^{-\alpha }}{\to }Y\stackrel{-\beta }{\to }Z\stackrel{-\alpha }{\to }A\stackrel{{}^{-\gamma }}{\to }P$ the atomic mass and atomic number of $P$ are, respectively

• A. 170, 69
• B. 172, 69
• C. 172, 70
• D. 170, 70

Answer 1

Answer: (B)

When an atom emits an $\alpha -$ particle its mass number deceases by 4 and atomic number by 2, when it emits a $\beta$ - particle its atomic number increases by 1, while there is no change in mass number and mass number and atomic number in $\gamma$-ray emission remains same.
${}_{72}{X}^{180}\stackrel{-\alpha }{\to }{}_{70}{Y}^{176}\stackrel{-\beta }{\to }$ ${}_{71}{Z}^{176}\stackrel{{}^{-\alpha }}{\to }{}_{69}{A}^{172}\stackrel{-\gamma }{\to }69^{172}$