Question

The nuclear radius of a certain nucleus is $7.2fm$ and it has a charge of $1.28\times {10}^{-17}C$. The number of neutrons inside the nucleus is:

• A. 126
  
• B. 111
  
• C. 118
  
• D. 142
  

Answer 1

The correct option is B 111

Radius of nuclear given by,

$R=RO{A}^{1/3}$ where $Ro=1.25fm$

$\Rightarrow A=(\frac{R}{Ro}{)}^3=(\frac{7.2}{1.25}{)}^3=191$ (atomic mass)

Now, no. of protons,

$Z=\frac{1.28\times {10}^{-17}}{1.6\times {10}^{-19}}=80$

Thus, no.of neutrons nuclears:

$N=A-Z=191-80=111$ (Ans)