On the periodic table, technetium was the first element to be artificially produced.
Technetium has atomic number 43 and symbol Tc. In 1937, Emilio Segrè and Carlo Perrier identified it in molybdenum foils that had been exposed to deuterons at the Lawrence Berkeley Laboratory cyclotron. The name comes from the Greek word technetos, meaning artificial.
Technetium filled a gap that had been predicted by Dmitri Mendeleev’s periodic classification. No stable isotope of technetium exists, so naturally occurring quantities on Earth are extremely small and usually result from uranium fission or radioactive decay.
Promethium was also first made artificially and has no stable isotopes, but its discovery came later. Technetium is therefore the standard answer to the historical “first artificial element” question.