<P> For stable nuclei, the neutron - proton ratio is such that the binding energy is at a local minimum or close to a minimum . </P> <P> From the liquid drop model, this binding energy is approximated by the semi-empirical Bethe--Weizsäcker formula </P> <Dl> <Dd> E B = a V A − a S A 2 / 3 − a C Z 2 A 1 / 3 − a A (A − 2 Z) 2 A ± δ (A, Z). (\ displaystyle E_ (B) = a_ (V) A-a_ (S) A ^ (2 / 3) - a_ (C) (\ frac (Z ^ (2)) (A ^ (1 / 3))) - a_ (A) (\ frac ((A-2Z) ^ (2)) (A)) \ pm \ delta (A, Z).) </Dd> </Dl> <Dd> E B = a V A − a S A 2 / 3 − a C Z 2 A 1 / 3 − a A (A − 2 Z) 2 A ± δ (A, Z). (\ displaystyle E_ (B) = a_ (V) A-a_ (S) A ^ (2 / 3) - a_ (C) (\ frac (Z ^ (2)) (A ^ (1 / 3))) - a_ (A) (\ frac ((A-2Z) ^ (2)) (A)) \ pm \ delta (A, Z).) </Dd>

How is nuclear stability related to the nuetron proton ratio