Question

What is a key difference between chemical and nuclear reactions?
In chemical reactions, new compounds are formed. In nuclear reactions, compounds are destroyed.
Chemical reactions involve electron rearrangements. Nuclear reactions involve changes to the nucleus.

Answer 1

The second statement is the key difference: chemical reactions involve rearrangements of electrons and chemical bonds, while nuclear reactions involve changes to the nucleus (protons and/or neutrons).

Brief consequences:
- Chemical reactions change how atoms are bonded (form or break compounds) but do not change the identity of the atoms (same elements, same nuclei). Energy changes are relatively small and come from electron-bond energies.
- Nuclear reactions change the nucleus (can change one element to another or convert isotopes), release or absorb much larger amounts of energy, and produce nuclear radiation or new particles.

The first statement ("In chemical reactions, new compounds are formed. In nuclear reactions, compounds are destroyed.") is misleading — compounds can be formed or broken in chemical reactions, and nuclear reactions may alter or destroy molecules as a side effect, but that is not the fundamental distinction.