Gallium elemental germanium

The person whose name is most closely associated with the periodic table is Dmitri Mendeleev (1836-1907), a Russian chemist. In writing a textbook of general chemistry, Mendeleev devoted separate chapters to families of elements with similar properties, including the alkali metals, the alkaline earth metals, and the halogens. Reflecting on the properties of these and other elements, he proposed in 1869 a primitive version of today s periodic table. Mendeleev shrewdly left empty spaces in his table for new elements yet to be discovered. Indeed, he predicted detailed properties for three such elements (scandium, gallium, and germanium). By 1886 all of these elements had been discovered and found to have properties very similar to those he had predicted. 

The action of alkyl halides on elemental germanium in the presence of a copper/gallium catalyst leads to the simultaneous preparation of several or all of the above-mentioned organogermanium halides248 ... 

Ans. Mendeleev had used the prefix eka- (Sanskrit word for first) to name elements whose existence he predicted, applying the prefix to a known element in the same periodic group as the predicted element. His eka-boron, eka-aluminum, and e a-silicon were later discovered, confirmed, and named scandium, gallium, and germanium. Elements 104 and 105 were predicted to have electronic structures analogous to Hf and Ta. 

Elemental germanium is used primarily in the preparation of semiconductors in which it is combined with phosphorus, arsenic, or antimony to make n-type semiconductors or with gallium to make p-type semiconductors. 

Mendeleev trusted the periodic law enough to leave gaps in his table for elements that were unknown at the time. He predicted the existence of the elements germanium, gallium. 

Subsequently, in 1860, Bunsen demonstrated that the colouring of the flames used as a means of identifying certain salts was due to the element and not the compound to which it was bound. The power of this new method led him to discover two unknown elements in mineral water caesium and rubidium. Other researchers then soon discovered thallium, indium, gallium and germanium, elements for which lines are emitted in the visible domain. 

Zinc (0.02% of the earth s crust) occurs almost entirely as ZnS this has two forms (Fig. 277), the much commoner cubic zinc blende or sphalerite, and the rarer, hexagonal wurtzite (p. 149). Iron and cadmium are nearly always present as substitutional impurities and the ore also serves to concentrate a number of much rarer elements such as indium, gallium and germanium. The sulphide is easily converted to oxide by roasting in air. 

The periodic table was devised by Mendeleev in response to observed regularities in the chemistry of the elements before there was any understanding of their electronic basis (see Topic A4). His procedure was vindicated by his ability to predict the properties and simple chemistry of the then unknown elements gallium and germanium by simple interpolation between known elements in neighboring positions. Chemical periodicity was thus seen to be a powerful tool in the interpretation and even prediction of the chemical properties of elements. 

In due course these elements were discovered and christened scandium, gallium and germanium respectively. They were found to possess properties remarkably close to those predicted by MendeteefF, and their discovery removed all lingering doubts as to the importance of the Periodic Law. 

Colorimetric measurements are carried out using a Varian 634 UV-VIS spectrophotometer. Gallium and germanium are the only elements determined in this fashion. 

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