What is nuclear energy?

• A. Energy released from the nucleus of an atom through nuclear fission, where a heavy atom's nucleus is split.
• B. Energy produced by burning fossil fuels.
• C. Energy from photons emitted by the Sun.
• D. Energy from chemical reactions between fuels and oxygen.

Answer: (A)

Nuclear energy comes from changes in the atomic nucleus, releasing energy when the nucleus is altered. The most common way we harness it is through nuclear fission, where a heavy nucleus splits into smaller nuclei and, in the process, releases a large amount of energy (and neutrons that can continue the reaction). This matches the statement describing energy released from the nucleus through fission. The other options describe energy from different processes: burning fossil fuels releases chemical energy from bonds between atoms, and energy from photons emitted by the Sun describes radiant energy, not energy released by changing the nucleus in a controlled nuclear process.