Why Are Nuclei with Excess Neutrons Unstable?

[Alexitron]

Hi there

First of all excuse my English.

My question is:

Why a nucleus with more neutrons than these in the valley of nuclear stability are not stable
and are beta(-)?

I know that a nucleus with high mass number have more neutrons than protons because the more the protons the higher the coulomb force but neutrons are not charged and can't add coulomb force in the nucleus.
So why Ge(32P,41N) is more stable than it's isotope Ge(32P,46N)
(which by the way has p&N even) ?

Thanks in advance.

 

[malawi_glenn]

Because the most favorable configuration is Ge(32P,41N) : you see, with your logic, Ge(32P,1187455N) would be more stable than Ge(32P,955N), and so on.

Neutrons are only 'feeling' the short ranged strong force, so there exists an upper limit for the number of neutrons a nuclei with a certain number of protons can bind. You can't just pack an arbitrary number of neutrons to a nucleus and make it stable. You can google for instance "neutron drip line" and read about it.

cheers