The first artificial transmutation of a nonradioactive element was achieved in 1919 by Ernest Rutherford. He found that on collision with an alpha particle (from a natural emitter), an atom of nitrogen was converted to an ion of oxygen and a hydrogen nucleus. In 1932, John D. Cockcroft and Ernest Walton achieved the first entirely artificial transmutation of an element by bombarding lithium with electrically accelerated protons. Attempts were made in the 1930s to produce a transuranium element by the bombardment of uranium with free neutrons. The unexpected result was the discovery of nuclear fission in 1938. Eventually, in 1940, E. M. McMillan and P. H. Abelson first positively produced and identified a transuranium element, which they named neptunium.
Transmutation is now a common process because of the availability of powerful particle accelerators and nuclear reactors, and virtually every element has been prepared artificially. More than 1,500 radioisotopes have been synthesized, many of which have valuable medical and industrial uses. The alchemists' dream is possible today: base metals can be transmuted to gold. The cost of the required energy, however, exceeds the value of the product.