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Friday, December 25, 2015

What is Covalent bonding?

The covalent bond is formed by sharing of pairs of valence electrons between like atoms rather than by electron transfer.
eg : consider the hydrogen molecule H2 ; when two isolated 'H' atoms, each with its electron in the ground state 1S orbital approach each other , the 1S clouds begin to overlap. Each electron is attracted to the other nucleus and the overlap increases( provided the electrons have opp spin) . The two atomic orbitals merge into a molecular orbital. when the repulsive forces have been balanced the attractive forces a molecule results , having stability greater than that of two isolated atoms.
The covalent bonding is also known as "Home polar" or "electron - pair bonding".

Saturation in covalent bonds
   Hydrogen molecule can be stable with only two atoms. If a third atom is brought near 'H2' it is repelled due to allowed exchange of spins is repulsive.Thus covalent bond exhibits.

Direction nature of Covalent bond
    The covalent bond is formed as a result of pairing of two electrons in the atomic orbitals of two atoms, the bond then should lie along the direction of overlapping of atomic orbitals.Hence covalent bonds will have strong preferences.

Hybrid bonding
         Covalent bonds are not only formed by pure 'S' orbitals or pure 'P' orbitals but can also be formed by the overlapping of 'S' and 'P' orbitals called hybrid bonding. eg:- H2O; The HOH bond angle is 104.5 deg