Question

In the nuclear reaction, ${ }_{72} X^{180} \xrightarrow{{ }^{-\alpha}}Y \xrightarrow{-\beta}Z \xrightarrow{-\alpha} A \xrightarrow{{ }^{-\gamma}} P$ 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.
${ }_{72} X^{180} \xrightarrow{-\alpha}{ }_{70} Y^{176} \xrightarrow{-\beta}$ ${ }_{71} Z^{176} \xrightarrow{{ }^{-\alpha}}{ }_{69} A^{172} \xrightarrow{-\gamma} 69^{172}$