When a Russian chemist named Dmitri Mendeleev laid out the sixty-three known chemical elements on a single sheet of paper in 1869, he deliberately left blank spaces for three elements he predicted would exist but had never been observed — and within the next seventeen years, all three were discovered exactly where he had left the gaps

When a Russian chemist named Dmitri Mendeleev laid out the sixty-three known chemical elements on a single sheet of paper in 1869, he deliberately left blank spaces for three elements he predicted would exist but had never been observed — and within the next seventeen years, all three were discovered exactly where he had left the gaps

The most consequential prediction in the recorded history of 19th-century chemistry was made by a Russian professor working on a textbook. Mendeleev had not set out to reorganise the fundamental structure of chemistry. He had set out, in the winter of 1868-1869, to complete the second volume of his textbook Principles of Chemistry (Основы химии) — a comprehensive Russian-language reference work that his students needed and that no comparable tex…