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РЕГИСТРАЦИЯ ЭКСКУРСИЯ

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~~The Structure of Covalent Compounds

 

The Structure of Covalent Compounds - раздел Образование, Part One THE PREDICATE The Clcctronic Structure Of Molcculcs Of Covalcnt Compounds Involving The Pri...

 
 

   

The clcctronic structure of molcculcs of covalcnt compounds involving the principal groups of the periodic table can usually be written by counting the number of valcncc electrons in the molcculc and then distributing the valcncc electrons as unshared electron pairs and shared electron pairs in such a way that cach atom achieves an argonic structure.

For many molcculcs the covalcncc of cach atom is equal to the number of unpaired electrons in its outer shell, and is, thus, simply related to the position of the clement in the periodic table. For other molecules and ions the covalcncc of the atoms is less simply related to the periodic table.

It is often ncccssary to have some experimental information about the way in which the atoms arc bonded together. Thus, there are two compounds with the composition C2H60: ethyl alcohol and dimethyl ether. The chcmical properties of these two substanccs show one of them, ethyl alcohol, to contain one hydrogen atom attached to an oxygen atom, whereas dimethyl ether doesn't contain such a hydroxyl group.

The atoms of most molcculcs are held tightly together by a very important sort of bond, the sharcd-clcctron-pair bond or the covalcnt bond. This bond is so important, so nearly universally present in substancc that Professor Gilbert Newton Lewis of the University of California (1876- 1946), who discovered its electronic structure, callcd it the chemical bond.

It is the covalcnt bond that is represented by a dash in the valcnce- bond formulas, such as

CI

I

Br—Br and CI — С — CI

I

CI

that have been written by chemists for over a hundred years.

Modern chemistry has been greatly simplified through the development of the theory of the covalcnt bond. It is now easier to understand and to remember chemical facts, by connecting them with our knowledge of the nature of the chemical bond and the electronic structure of molcculcs, than was possible at the beginning of the ccntury.

 


19.01.2015; 01:18
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