Saturday, 17 January 2015

Chemical Bonds


Formation of chemical bonds

With the term chemical bond is globally indicate interactions between atoms that lead to formation of molecules or even to the formation of ionic crystals or crystals of metallic type. These interactions are mainly the outer electrons of atoms and produce changes in the electronic structure of atoms.

The fundamentals of electronic theory of the chemical bond are based on the model of GN Lewis that the binding affects only the outer electrons of atoms: each atom tends to complete the orbital of the outermost level (and therefore to have eight valence electrons) is taking or giving electrons, is putting electrons in common. But a satisfactory understanding of the nature of the chemical bonds is achieved only with hypotheses that take account of quantum mechanics: these theories originated by two distinct approaches, the method of valence bond and molecular orbital method.
Classification of the chemical bonds

Types of chemical bonds:

1 Covalent bond

The covalent bond is formed between atoms that have a high value of electro negativity between atoms and therefore "non-metallic". There are two types of covalent bond: the covalent bond and the pure polar covalent bond.

The pure covalent bond (covalent or homopolar) occurs between atoms of the same element.

The polar covalent bond (covalent or heteropolar) occurs between atoms of different elements (but 
the two atoms must have a difference of electro negativity of less than 1.9).

In reality, there is also a special type of covalent bond called dative bond in which an atom donor or said employer provides the pair of bonding electrons. This pair of electrons is shared with an atom acceptor said. This bond once formed is not distinguishable from a normal covalent bond.

2 Ionic Bond

Ionic bonding is achieved when the difference in electro negativity between the two elements that intend to bind is greater than 1.9. Occur the transfer of one or more electrons from the less electronegative atom more electronegative. The metallic bond holds together the atoms of a metal.