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Referat HYDROGEN COMPOUNDS OF THE GROUP IV ELEMENTS

HYDROGEN COMPOUNDS OF THE GROUP IV ELEMENTS

Categorie: Referate Engleza

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Hydrogen compounds of group IV elements The IVth group of the periodic system contains the elements: C, Si, Ge, Sn, and Pb. Carbon. Man has known carbon, as charcoal from the combustion of wood, from prehistoric times. Its name derives from the Latin "carbo" meaning charcoal. The element is unique in the vast number of its compounds- there are probably more than one million known today. Carbon is widely distributed throughout the universe. Much of the energy of the sun and stars is due to the carbon cycle. Both black and transparent diamonds have been found in meteorites. The cosmic abundance is six times that of silicon. The name of this element derives from a corruption of the Greek word "adamas" meaning invincible. Combined with hydrogen, carbon occurs extensively as coal, petroleum and natural gas. In spite of its wide spread occurrence carbon still only constitutes 0.027% of the earth's crust. The distribution of terrestrial carbon is approximately as follows: minerals-99.7%, atmosphere-0.2%, and living matter-0.01%. Even if combining with hydrogen is very difficult to achieve, a great number of hydrides of carbon is known which is the object of organic chemistry. The hydrides of carbon are covalent compounds. Carbon possesses in the valence shell four electrons and forms four bonds in almost all of its combinations. The bonds of carbon aren't made with the pure orbitals 2s2p, but with some hybrid tetrahedral orbitals. The saturated hydrides of carbon don't have an acid character, which means that don't have the tendency to loose protons. In a period this tendency increases from the 4th to the 7th group. So in the series: H H H H:C:H H:N:H :O:H :F:H H HF gives easily the proton to water and forms ions like F

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