Why is there ever a need for a beta minus decay, when the more strong nuclear force a nucleus has, the more stable it is?

Question

My textbook says that: “in stable isotopes, strong nuclear forces are greater than the electrostatic forces”.

Doesn’t that imply that, the more neutrons a nucleus has, the stronger this strong nuclear force will get, so it’s always a win if we have more neutrons?

The definition of beta decay is also stated as “occurs if the nucleus has too many neutrons to be stable”. How and when would this ever be a case? The two definitions seem contradicting

In: Physics

Answer 1

Your conclusion from the text book paragraph is incorrect. All that statement says is “stable isotopes are stable because the strong nuclear force is larger than the electrostatic force” you forget that the strong force drops off very quickly with distance, so adding more and more neutrons decreases the overall strong force, making the electrostatic force become more dominant.