The compound unstabel nucleus `._(92)^(236)U` often decays in accordance with the following reaction
`._(92)^(236)U rarr ._(54)^(140)Xe +._(38)^(94)Sr ` + other particles
During the reaction, the uranium nucleus ''fissions'' (splits) into the two smaller nuceli have higher nuclear binding energy per nucleon (although the lighter nuclei have lower total nuclear binding energies, because they contain fewer nucleons).
Inside a nucleus, the nucleons (protonsa and neutrons)attract each other with a ''strong nuclear'' force. All neutrons exert approxiamtely the same strong nuclear force on each other. This force holds the nuclear are very close together at intranuclear distances.
Why is a `._2^4He` nucleus more stable than a `._3^4Li` nulceus?

Options

A. The strong nuclear force is larger when the neutron to proton ratio is higher.
B. The laws of nuclear physics forbid a nucleus from contaning more protons than neutrons.
C. Forces other than the strong nuclear force make the lithium nulceus less stable.
D. None of the above.

Answer

a

Explanation

According to the passage, all nucleons attract each other with the same strong nuclear force. So, the strong nuclear forceholds together three protons and one neutron `(._3^4Li)` just as vigorously as it holds together two protons and two neutrons `(._2^4He)`. But other forces play a role, too. Specifically, protons electrostatically repel other protons. This repulsion 'tries' to make a nucleus fly apart. Since `(._2^4He)` contains only two protons, the attractive strong nuclear force overcomes the repulsion of the protons.Therefore, the nulceus holds together. But in `(._3^4Li)`, 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).