Answer
See explanation
Work Step by Step
If Mass number A = number of protons + neutrons and Z = number of protons, the ratio A/Z is:
- for light, stable isotopes:
𝐴/𝑍$\approx$ 1-2
- for heavy, stable isotopes:
𝐴/𝑍>2, increasing gradually with atomic number
So for lighter elements in stable isotopes, the mass number to the atomic number ratio is close to 2. This ratio increases as the stable isotopes becomes heavier.
Reason: heavier nuclei require more neutrons than protons to remain stable against electrostatic repulsion between protons.
