Final answer:
Nuclear reactions alter the nucleus and release significantly more energy compared to chemical changes, which deal with electron arrangements and less energy release.
The correct option is a), highlighting these major distinctions.
Step-by-step explanation:
The two principal differences between nuclear reactions and ordinary chemical changes are that nuclear reactions involve changes in the atom's nucleus and release much more energy, whereas chemical changes involve the rearrangement of electrons and release less energy.
Therefore, the correct answer is a) Nuclear reactions involve changes in the nucleus, release more energy; chemical changes involve electrons, release less energy.
In nuclear reactions, the stability of an atom's nucleus is affected, often leading to the production of a different element.
These nuclear processes can emit heat, light, and radiation due to changes in nuclear binding energy, which are significantly higher than energies involved in chemical reactions.
On the other hand, chemical reactions are linked with electron movements and deal with breaking or forming of chemical bonds without altering the nuclei of the atoms.