Question

defining nuclear energy. nuclear energy is the energy stored in the of an atom. nucleus electrons protons

Explanation:

Nuclear energy is associated with the nucleus of an atom. The nucleus contains protons and neutrons, and energy is released through nuclear reactions like fission or fusion which occur in the nucleus. Electrons are involved in chemical reactions, not nuclear energy storage. Protons are just part of the nucleus, and the overall energy - storing entity relevant here is the nucleus.

Answer:

nucleus