The periodic table of the elements—the venerable icon of chemistry found today in classrooms throughout the world and in many of our purses and wallets—was devised in 1869 by the eximious Russian chemist Dmitri Mendeleev (1834–1907). Several individuals before him, including Döbereiner, Newlands, de Chancourtois, and Meyer, had come up with alternative proposals to organize the chemical elements known at the time. However, Mendeleev’s key to success was to reserve empty spaces in his classification and even predict the basic physical and chemical properties for elements yet to be discovered, including those he tentatively named ekaaluminum, ekaboron, and ekasilicon. Within a few years, the discovery of gallium by Paul Emile Lecoq de Boisbaudran (1875), scandium by Lars Nilson (1879), and germanium by Clemens Winkler (1886), validated his predictions and brought his periodic table widespread recognition.
The stamp that illustrates this note was issued on 2 February 2007 in Spain to commemorate the 100th anniversary of Mendeleev’s death. In an attractive design reminiscent of a Piet Mondrian composition, the stamp depicts with different colors the four main neighborhoods in the periodic table that separate the elements by their electron configurations (i.e., the s-, p-, d- and f-blocks). The stamp also shows four white boxes or “holes” for the elements lighter than the rare earths whose existence was predicted by Mendeleev in 1869. Interestingly, although the discovery of gallium, scandium, and germanium catalyzed Mendeleev’s ascent to posterity, the isolation of his ekamanganese would have to wait almost seven decades, until 1937, when Carlo Perrier and Emilio Segrè at the University of Palermo isolated technetium, the first artificial element and the only radioactive transition metal.
Written by Daniel Rabinovich <email@example.com>.
The designer of the stamp—Javier García Martínez—is an active IUPAC member and a professor of inorganic chemistry at the University of Alicante in Spain. Not many chemists (or IUPAC members) get involved in postage stamp designing!