Question

when is said to be nucleus unstable

Answer 1

the nucleus is said to be unstable when the neutron proton ration in it increases than 1. it is tolerable upto 1.1 or 1.2, but above that the nucleus is said to be unstable and the atom becomes radioactive. for eg U-235

Answer 2

Answer:

it is the balance of protons and neutrons

in a nucleus which determines whether a

nucleus will be stable or unstable. too many neutrons or protons upset this balance disturbing the binding energy from the strong nuclear forces making the nucleus unstable.