Which isotopes of aluminum are radioactive?
You might get a better answer on the physics forum, but AFAIK radioactivity is not related to unequal numbers of nuclear protons and neutrons.
The common radioactive isotope of
As said, radioactivity is not related to unequal numbers of protons and neutrons, but a non optimal combination of both or an excess of energy (metastable). Protons are positvely charged and repel each other. The more protons you try to fit into the nucleus (higher Z-values) the more neutrons you need to keep them together. You can see neutrons as the glue of the nucleus.