A) 136
B) 142
C) 140
D) 132
E) 126
Correct Answer: A
Solution :
\[R={{R}_{0}}{{A}^{1/3}}\] Here, \[R=7.2\times {{10}^{-15}}m,{{R}_{0}}=1.2\times {{10}^{-15}}m\] \[\therefore \]\[A={{\left( \frac{R}{{{R}_{0}}} \right)}^{3}}=\left( \frac{7.2\times {{10}^{-15}}}{1.2\times {{10}^{-15}}} \right)={{(6)}^{3}}=216\] Also, atomic number\[Z=\frac{q}{e}=\frac{1.28\times {{10}^{-17}}}{1.6\times {{10}^{-19}}}=80\] Therefore, number of neutrons \[N=A-Z=216-80=136\]
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