Scandium atomic weight

Aston EW (1932) The isotopic constitution and atomic weights of cesium, strontium, lithium, rubidium, barium, scandium and thallium. Proc Roy Soc A 134 571 Bach RO (ed) (1985) Lithium—Current Applications in Science, Medicine, and Technology. Wiley-Interscience, New York... 

The discovery of gallium was followed by the discovery of scandium (Mendeleev s eka-boron) in 1879 and of germanium (eka-sili-con) in 1886. The new elements had the approximate atomic weights and properties that Mendeleev had predicted. The scientific world was astonished. It is probably safe to say that before Mendeleev s predictions were confirmed, no chemist would have believed that the properties of unknown elements could be predicted with such accuracy. 

After commenting on the discovery of gallium, scandium, and germanium (eka-aluminum, eka-boron, and eka-silicon), D. I. Mendeleev had written in 1891, I foresee some more new elements, but not with the same certitude as before. I shall give one example, and yet I do not see it quite distinctly (7). He had then proceeded to describe an undiscovered dvi tellurium with an atomic weight of about 212. Since polonium resembles tellurium and has an estimated atomic weight of about 210, it is probably the realization of Mendeleev s dvi tellurium. ... 

Cdtium was isolated from the soluble end of a series from gadolinite by fractional crystallization of the nitrates in nitric add. Its compounds have properties intermediate between those of scandium and lutecium. Its atomic weight has not been determined, but the atomic number 72 has been assigned to this element. The discovery of hafnium, a close relative of... 

Oxides of the type RjO arc formed by all rare earth elements, by the ignition of the hydroxide, nitrate, sulfate, carbonate, or oxalate. In general the basicity decreases with increase of atomic weight, though yttrium and scandium are exceptions to the rule. The basicity of lanthanum approaches that of the alkaline earths, while scandium is about as basic as aluminium. 

The most famous of Mendeleev s predictions involved eka-boron (scandium), eka-aluminium (gallium), and eka-silicon (germanium). For example, for eka-silicon he predicted its atomic weight, its density, the compounds it would form, and details about their physical properties. When thirteen years later germanium was discovered and it was determined that Mendeleev s predictions had been correct, scientists began to recognize the importance of the Periodic Table, and its discovery was quite naturally associated with Mendeleev, who encouraged this association. 

For many years an atomic weight of 44 1 was accepted for scandium, but in 1923 Aston showed that the element had no isotopes and that its atomic mass relative to oxygen 16 was 45. As a result of fresh chemical investigation, the atomic weight 45 1 was accepted by the International Committee in 1925, and this value is accepted to-day (1950). 

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