Chemical Bonding:- The attractive force which holds various constituent ( atoms,ions,etc.) together in Chemical species is called a Chemical Bond.
1. Tendency to acquire minimum energy
a). When two atoms approach to each other - nucleus of one atom attracts the electrons of another atom.
b). Two nuceli and electrons of both the atoms repell each other.
c). If net results is attraction,then the total energy of the system ( molecule ) decreases.A Chemical bond is formed when the net energy of system is least.
d). The amount of energy released during bond formating is know as ' Bond Energy '.
2. Tendency to acquire noble gas configuration ( octet rule ).
Atoms combine to complete an octet of electrons in their outer most shell. Hence all atoms have a tendency to acquire octet ( s2p2) configuration or to attain nearest noble gas configuration in their outermost orbit. This can be achieved by combining with other atom or ion.
* Exceptions to Octet Rule
1). Hypovalent:- Less than 8 electrons in valance shell of Central ATOM. Phenomenon is called contraction of octet.