In 1875 the French scientist Paul Emile Lecoq de Boisbaudran made an important report to his colleagues. He had succeeded in detecting an admixture of a new element in a zinc ore, a tiny grain weighing not more than a gram. Being an experienced investigator, he studied the properties of gallium (such was the name of the "newborn" element) in all their aspects, and wrote a paper about them.

   Some time passed and the post brought de Boisbaudran an envelope bearing a St. Petersburg postmark. In the brief letter the French chemist read that his correspondent agreed in full with his results, except for one detail: the specific gravity of gallium should be 5.9 instead of 4.7. The letter was signed: D. Mendeleyev.

   Lecoq de Boisbaudran was worried. Had the Russian titan of chemistry anticipated him in the discovery of the new element?
No, Mendeleyev had not had gallium in his hands. He had simply made efficient use of the Periodic System.

   Mendeleyev had long since known that sooner or later an unknown element would be found to take the place in the table, which was now occupied by gallium. He had given it the preliminary name of eka-aluminium and had predicted its chemical nature very accurately, knowing the properties of its neighbours in the Periodic Table.

   So Mendeleyev became the first "programmer" in chemistry. He predicted almost a dozen other then unknown elements, and described their properties more or less completely. Their present names are: scandium, germanium, polonium, astatine, hafnium, rhenium, technetium, francium, radium, actinium, and protactinium. Most of them had actually been discovered by 1925.

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