Final answer:
Nuclear reactions involve changes in an atom's nucleus and can alter the element itself, releasing energy from nuclear binding energy, whereas chemical reactions only involve rearrangement of electrons and depend on interatomic and intermolecular forces. Nuclear reactions release energy on a much grander scale than chemical reactions and are not affected by environmental conditions.
Step-by-step explanation:
Nuclear reactions and chemical reactions differ significantly in where they occur within an atom. Chemical reactions involve changes in the electronic structure, specifically the arrangement of electrons surrounding atoms, ions, or molecules. These reactions take place in the outermost areas of an atom, known as the valence shell, and do not result in the alteration of the atomic nuclei. The energy involved in chemical reactions is associated with the movement of electrons between energy levels, typically on the order of 1 x 10³ kJ/mol.
Conversely, a nuclear reaction entails changes in the nucleus of an atom and often leads to the transformation of elements. These reactions can either split a nucleus apart in fission, combine two nuclei together in fusion, or convert neutrons into protons and vice versa in radioactive decay. Nuclear reactions are independent of the chemical form of the element and the energy changes involved are vastly greater. This is because the energy originates from nuclear binding energy, rather than electron movements, and can reach magnitudes of approximately 1 × 10¹⁸ kJ/mol. The reactions release massive amounts of energy as heat, light, and radiation, sometimes even causing a measurable change in mass as some mass is converted into energy according to Einstein's famous equation E=mc².
The energies released in nuclear reactions are therefore almost one million times greater per atom than those in chemical reactions. Nuclear reactions also do not depend on environmental conditions such as temperature or pressure, which can significantly influence chemical reactions.