The mass number of sodium is 23, and the radius of a sodium atom is about 1.86 × 10⁻¹⁰ m…

Step 1. Nucleus. $R = 1.2 \times 2.84 = 3.41\ \text{fm} = 3.41 \times 10^{-15}\ \text{m}$.

Step 2. Radius ratio. $\dfrac{1.86 \times 10^{-10}}{3.41 \times 10^{-15}} = 5.45 \times 10^{4}$.

Step 3. Volume ratio. $(5.45 \times 10^{4})^3 = 1.6 \times 10^{14}$.