Is the force between protons in the nucleus attractive or repulsive

Inside the nucleus, the attractive strong nuclear force between protons outweighs the repulsive electromagnetic force and keeps the nucleus stable. Outside the nucleus, the electromagnetic force is stronger and protons repel each other.

Explanation:

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.