Answer the following question given this paragraph: 

The strong nuclear force works only over very short distances. As a result, it isn’t effective if the nucleus gets too big. As more protons are added to the nucleus, the electromagnetic force of repulsion between them gets stronger, while the strong nuclear force of attraction between them gets weaker. This puts an upper limit on the number of protons an atom can have and remain stable. If atoms have more than 83 protons, the electromagnetic repulsion between them is greater than the strong nuclear force of attraction between them. This makes the nucleus unstable, or radioactive, so it breaks down. The following video discusses the strong nuclear force and its role in the atom. The video also introduces the weak nuclear force, which is described next.


Q: If the electromagnetic repulsion between protons is greater than the strong nuclear force of attraction between them, what do they become?


A:
unstable, or radioactive