compared to the energy released per mole of reactant during chemical reactions, the energy released per mole of reactant during nuclear reaction is

Copper, silver, aluminum, cobalt, chromium, mercury 

They are all full and don't need any more electrons in there outer shell.

The atomic nucleus made up from protons (yellow) and neutrons (blue) and held together by nuclear forces. nuclear forces (also known as nuclear interactions or strong forces) are the forces that act between two or more nucleons. they bind protons and neutrons (“nucleons”) into atomic