Question

The radius of Ge nuclide is measured to be twice the radius of \({}_4^{}B{e^9}\). The number of nucleons in Ge are
1. 71
2. 72
3. 73
4. 74

Answer 1

Correct Answer - Option 2 : 72

The correct answer is 72.

R ∝ A1/3 ;where, 

R= radius of the atom ;and 

A= number of nucleons or mass number

\(\dfrac{R_{Be}}{R_{Ge}} = \dfrac{A_{Be}^{1/3}}{A_{Ge}^{1/3}}\)

or \(\dfrac{1}{2} = \dfrac{9^{1/3}}{A_{Ge}^{1/3}}\)

or \(\dfrac{1}{8} = \dfrac{9}{A_{Ge}}\) (taking cube on both sides)

or \(A_{Ge} = 8 × 9\)

or AGe = 8 × 9 = 72 nucleons.