TRIPLE COVALENT BOND : A covalent bond formed by the mutual sharing of three pair of electrons is called a triple covalent bond , or simply a triple bond . A triple covalent bond is represented by three small horizontal lines ( ≡ ) between the two atoms . E . g . N≡N , H-C≡C-H etc .
FORMATION OF A COVALENT BOND : Formation of a covalent bond is favored by
( i ) High ionisation enthalpy of the combining elements .
( ii ) Nearly equal electron gain enthalpy and equal electro-negativities of combining elements .
( iii ) High nuclear charge and small atomic size of the combining elements .
POLAR COVALENT BOND : The bond between two unlike atoms which differ in their affinities for electrons is said to be polar covalent bond . E . g . H-Cl
COORDINATE BOND : The bond formed when one sided sharing of electrons take place is called a coordinate bond . Such a bond is also known as dative bond . It is represented by an arrow ( → ) pointing towards the acceptor atom . E . g . H3N→BF3
Bond Length : Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule
Bond Angle : It is defined as the angle between the orbitals containing bonding electron pairs around the central atom in a molecule / complex ion
Bond Enthalpy : It is defined as the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state .
Bond Order : In the Lewis description of covalent bond , the Bond Order is given by the number of bonds between the two atoms in a molecule
Resonance : whenever a single Lewis structure cannot describe a molecule accurately , a number of structures with similar energy , positions of nuclei , bonding and non-bonding pairs of electrons are taken as the canonical structures of the hybrid which describes the molecule accurately