For example Ethyne - C2H2: In the formation of ethyne both the carbon atoms undergo 'sp' hybridisation leaving two unhybridised orbitals on each (2py and 2pz). One 'sp' hybrid orbital of one carbon atom overlaps axially with the 'sp' hybrid orbital of the other carbon atom to form C-C sigma bond. The remaining hybridised orbital of each carbon atom overlap axially with half filled orbital of hydrogen forming sigma bond. Each of the two unhybridised orbitals of one carbon atom overlaps sidewise with the similar orbitals of the other carbon atom to form two pi bonds.

Structure and Bonding

Page 1

Type of hybridisationNumber of orbitals usedNumber of unused p-orbitalsBondBond angleGeometry% s-character

sp31s and 3pNilFour -109.5Tetrahedral25 or 1/4

sp21s and 2pOneThree - One -120Trigonal33.33 or 1/3

sp1s and 1pTwoTwo - Two -180Linear50 or 1/2

Bond Parameter

i) Bond length: Bond length is defined as the average equilibrium distance between centers of the nuclei of the two bonded atoms in a molecule. Since the bond length is a very small quantity so it is expressed in angstrom unit or picometer unitEach atom of the bonded pair contributes to the bond length and in case of a covalent bond the contribution from each atom is called the covalent radius of that of that atom.Factors affecting the Bond length A. Atomic size: more the size of the bonded atoms more the bond length for ex. HI> HBr> HCl