Question

Why is a ${}_2^{4}He$ nucleus more stable than a ${}_3^{4}Li$ nucleus?

• A. The strong nuclear force is larger when the neutrons to proton ratio is higher.
• B. The lows of nuclear physics forbid a nucleus from containing more protons than eutrons.
• C. Forces other then the strong nuclear force make the lithium nucleus less stable.
• D. None of the above.

Answer 1

The correct option is C Forces other then the strong nuclear force make the lithium nucleus less stable.

According to the passage, all nucleons attract each other with the same strong nuclear force. So, the strong nuclear force holds together three protons and one neutron ${}_3^{4}Li$ just as vigorously as it holds together two protons and two neutrons ${(}_2^{4}He)$. But other forces play a role, too. Specifically, protons electrostatically repel other protons. this repulsion tries to make a nucleus fly apart. Since ${}_2^{4}He$ contains only two protons, the attractive strong nuclear force overcomes the repulsion of the protons. Therefore, the nucleus holds together. But in ${}_3^{4}Li$, the mutual repulsion of the three protons overcomes the strong nuclear attraction, and the nucleus falls apart. (or undergoes radioactive decay into a more stable nucleus)