Atomic mass unit is a term used to describe the mass of a neutral atom of a nuclide.
Atomic energy is a term used to describe the constitutive internal power of the atom, which was absorbed when formed.
Nuclear fusion reactors is a term used to describe a future source of energy. Most stars including our own Sun released energy by nuclear reactions between light atoms at temperatures of millions of degrees.
Element (chemical) is a term used to describe a substance that cannot be broken down into two or more new substances by chemical or physical processes
Atomic number symbol