Discus of Covalent bond

Covalent bond

In the simple view of a so-called Covalent Bond, one or more electron (often a pair of electrons) are drawn into the space between the two atomic nuclei. Here the negatively charged electron are attract to the positive charged electrons are attract to the positive of both nuclei, instead of just their own. This overcomes the repulsion between the two positively charged nuclei of the two atoms, and so this overwhelming attraction holds the two nuclei in a fixed configuration of equilibrium, even though they will still vibrate at equilibrium position. Thus, covalent bonding involves sharing of electrons in which the positively charged nuclei of two or more atoms simultaneously attract the negatively charged electrons that are being shared between them. These bonds exist between two particular same or different atoms, and have a direction in space, allowing them to be shown as single connecting lines between atoms in drawings. For Example, Two chlorine atoms react to form a Cl₂ molecule.

 Each chlorine atom gives a share of its electrons to other atom. A pair of electrons is shared equally between both atoms and each atom now has eight electrons in its outer shell (stable octet). In a similar way a molecule of tetra chloro-methane CCl₄ is made up of one carbon and four chlorine atoms.          

The carbon atom is short of four electrons so as to have noble gas structure. Consequently, it forms four bonds with the chlorine atom which themselves are short of one electron so they each form one bond. By sharing electrons in this way both carbon and all four chlorine atoms attain a noble gas structure.

A molecule of ammonia NH₃ is made up of one nitrogen and three hydrogen atom

Other example of covalent bonds includes water (with two covalent bonds) and hydrogen – fluoride (one covalent bond and three long pairs.)

  

 

In a polar covalent bond, one are more electrons are unequally shared between two nuclei. Covalent bonds often result in the formation of small collections of better-connected atoms call molecule. These molecule in solid and liquid state are bound to other molecules by inter-molecular forces that are often much weaker than the covalent bonds that hold the molecules internally together. Such weak inter-molecular bonds give organic molecule substances, such as waxes and oils, their soft bulk character, and their low melting (in liquid, molecule must case most structured or oriented contact with each other). When covalent bonds link long chain of atoms in large molecule however (as in polymers much as nylon), or when covalent bonds extend in networks through solid that are not composed of discrete molecule (such as diamond or quartz or the silicate minerals in many type of rock) then the structures that result may be both strong and tough, at least in the polymers and networks increase greatly.