Do you think it will ever be possible to build/create different atoms up to carbon or perhaps even gold (the alchemist’s dream)? You would have to use fusion, wouldn’t you? Would this be a good source of energy? — JB, Norman, OK
As you noted, this process of sticking together smaller atomic nuclei or nuclear fragments to form larger atomic nuclei is called fusion. Many smaller nuclei release energy when they grow via fusion, so long as the resulting nuclei are no larger than 56Fe (the nuclei of a normal iron atom). Above that size, energy is consumed in the process of sticking the nuclei together. So building carbon nuclei would release energy and building gold atoms would require energy. But while it’s possible to construct atomic nuclei up to carbon or even gold, it isn’t very practical. It’s very difficult to bring atomic nuclei close to one another because they are all positively charged and repel one another fiercely. Because the nuclear energy these nuclei release during fusion only emerges at the moment they actually touch, something must push them together for that to occur. The nuclei can be pushed together by (1) nuclear fission reactors, (2) particle accelerators, (3) thermonuclear weapons, (4) giant lasers, or (5) thermal fusion reactors. None of these systems is ready to synthesize large quantities of normal atoms in a cost effective manner (although nuclear fission reactors do produce useful quantities of radioactive isotopes) and none is ready to produce practical energy from fusion processes.