In a prestigious Faraday Lecture to the Royal Institution in London in 1889, he admitted that he had not expected to live long enough ‘to mention their discovery to the Chemical Society of Great Britain as a confirmation of the exactitude and generality of the periodic law’. Mendeleyev himself was surprised by how fast his ideas were confirmed. Within twenty years, all three had been found, and their properties confirmed his predictions almost exactly. So convinced was he of the soundness of his periodic law that he left gaps for these elements in his table. Soon, Mendeleyev was predicting the properties of three elements – gallium, scandium and germanium – that had not then been discovered. Now each chemical element had its number and fixed position in the table, and from this it became possible to predict its behaviour: how it would react with other elements, what kind of compounds it would form, and what sort of physical properties it would have. Mendeleyev’s ideas totally changed the way chemists viewed their discipline. It was perhaps the greatest breakthrough in the history of chemistry. He wrote down the sequence in such a way that they ended up grouped on the page according to known regularities or ‘periodicities’ of behaviour. On 17 February 1869, Mendeleyev jotted down the symbols for the chemical elements, putting them in order according to their atomic weights. When the French novelist Balzac wrote ‘without numbers, the whole edifice of our civilisation would fall to pieces’, he might have been anticipating an insight by the Russian chemist Dmitri Mendeleyev.
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