As we go from light atoms to heavier ones, (a) What happens to the neutron-to-proton ratio? (b) Why does the answer to part (a) make sense?

As we move from lighter atoms to heavier ones, we notice that the number of neutrons in the heavier atoms is generally larger than the number of protons. Consequently, the neutron-to-proton ratio (N/Z) increases, where N is the number of neutrons and Z is the number of protons.

The increase in the neutron-to-proton ratio for heavier atoms can be explained by considering the forces acting within atomic nuclei: 1. Attractive strong nuclear force: This force acts between nucleons (protons and neutrons) at very short ranges and holds the nucleus together. 2. Repulsive electrostatic force: This force acts between the protons in the nucleus due to their positive charge, creating a repulsion force that tries to break the nucleus apart. For lighter atoms, the strong nuclear force is sufficient to overcome the electrostatic repulsion between the protons. As we move to heavier atoms with more protons, the repulsive force between them increases. To keep the nucleus stable, we need more neutrons since they don't contribute to the repulsive electrostatic force while still participating in the strong nuclear force, binding protons together. The increasing neutron-to-proton ratio in heavier nuclei helps to balance the strong nuclear force and the electrostatic repulsion in the nucleus, contributing to the stability of the atom.