The size of a nucleus (its radius and volume) is related to the mass number \(A\). Experiments show that all nuclei are approximately spherical and have radii proportional to the cube root of \(A\), or \(A^{1/3}\):
This equation states that if we increase the number of nucleons in a nucleus by a factor of 10, say from \(A = 20\) to \(A = 200\), the radius of the nucleus will increase by a factor of \(10^{1/3}= 2.2\) (Figure 27-3).