Question

Statement I: Neutron to proton ratio less than 1 especially in a heavy nucleus makes it highly unstable.
Statement II: Nucleus where protons are separated by a large distance are dominated by repulsive electrostatic force.

• A. Both statements are always true and statement II is the correct reason for statement I
• B. Both statements are false
• C. Statement I is not always true but II is correct.
• D. Statement I is false but II is true.

Answer 1

The correct option is A Both statements are always true and statement II is the correct reason for statement I

Strong nuclear force is a short ranged force. It's very strong in that range though.

From the above graph we see that in nature there doesn’t exists any heavy nucleus that has $\frac{N}{P}$ <1.
You remember we spoke about strong nuclear force only being stronger in a particular range after which the electrostatic repulsion takes over.
In heavier nucleus where the diameter increases more than 4 nucleons then this phenomenon starts to happen.
Take 2 protons on the opposite end of such a heavy nucleus. Now they won't attract each other as the strong nuclear force has less effect in this range but they will still repel each other by electrostatic repulsion which will try to break the nucleus apart.
Now imagine such big nuclei with mostly protons. $\frac{N}{Z}$ <1.
Is it possible for it to exist without decaying?