Abstract

Dmitri Mendeleev’s detailed prediction in 1871 of the properties of three as yet unknown elements earned him enormous prestige. Eleven other predictions, thrown off without elaboration, were less uniformly successful, thanks mainly his unbending adherence to the structure of his table and his failure to account for the lanthanides. At the end of his life he returned to his table without making the required changes, and added a theoretical discussion of elements lighter than hydrogen. The overall balance of success and failure is nevertheless in his favour. There may now be a similar failure to understand the ultra-heavy elements because of adherence to the pattern of chemical groups.