Relativity rewrites the textbook take on triple bonds, experiments on carbon–bismuth ion prove

Triple bonds take on a very different shape in heavier atoms where relativistic quantum effects are at play, researchers in the US have found. The researchers say their spectroscopic study on the triple-bonded CBi^– anion shows how molecular orbitals mix together, as predicted by theory, but also reveals unexpected differences that raise important questions about bonding in heavier atoms.