To be or not to be: the early history of H3 and H3+

Triatomic hydrogen became a major research area only after 1980, but its history goes back to J.J. Thomson's discovery in 1911. In fact, the possible existence of H-3 was suggested as early as 1895. This paper outlines the history of H-3 and H-3(+) up to the mid-1930s, when chemists and physicists ceased to believe in the existence of the H-3 molecule. In the intervening years, there was a great deal of interest in 'active hydrogen' and also in the configuration of H-3, which was examined by Bohr in 1919. While H-3 was abandoned, H-3(+) was not. Although the properties of H-3(+) were largely unknown, the existence of the ion was firmly established, and its structure studied by means of the new methods of quantum chemistry.