CHEMICAL BOND

CHEMICAL BOND:-

Force which hold together two or more than two or more than two atoms or ions to form a large variety of compounds is known as chemical bond. These forces are responsible for the bonding and shape of molecules as shown in fig 

CAUSE OF CHEMICAL COMBINATION OR FORMATION OF CHEMICAL BONDS:-

Almost every atom have incomplete valence shell and have some unpaired electrons in there outer most shell which are responsible for formation of chemical bonds these unpaired electrons make electron unstable. All elements combine with one another  other to stabilize them selves. They get stabilized by losing or gaining or sharing electrons to make their outer most shell completely filled as shown in the fig. There exist an exception of elements of group VIII-A which have there outer most shell complete filled and have no unpaired electrons which represents that group VIII-A elements are stable and they don't react easily that is why they are called noble gasses eg He 1s² or Ne, Ar, Kr etc which have electronic configurations ns²,np⁶ . There are just few stable compounds of noble gases eg XeF₂, XeF₄, XeOF₂, XeO₃ etc

       

 ENERGIES OF BOND FORMATION:-

The amount of energy required for the formation of one mole of any gas is called energy of bond formation. According to modern theories of chemical bonding atoms form bond as it leads to decreases in potential energy and make them stable. For example consider two hydrogen atoms which are unstable and has maximum potential energy to form bond. These two hydrogen atom approaches each other , forces of attraction and repulsion operates simultaneously. As the atoms approach each other, the electron concentration between the nuclei and attraction occurs. Hence the potential energy decreases. At a very short distance the electrons would be squeezed out as a result the two positively charged nuclei will experience a repulsive force due to each other. This result in the curve rising as r further decreases as shown in the graph. At r_o energy between the atom is lowest. This point has greatest stability for the molecule. Hence r_o, known as equilibrium spacing of atom, gives the average separation between the atoms in the molecules which also provides us the information about the bond length that is distance between the two atoms in a molecule. In present case it is 74 pm. Electrostatic force between the atom at equilibrium separation is zero and at this position hydrogen atom is stabilized to maximum extent. The amount of energy evolved is 432 KJ/mol and is called energy of bond formation. In order to break the bond same amount of energy is required.