Скачать или смотреть Chemical Bonding II Valence shell Electron pair repulsion theory II Lec 10 II Class 10 CBSE and ICSE

In this lecture concept of Valence shell electron pair repulsion theory is discussed.

octet rule was able to explain molecular structure but not able to explain geometry and shape of the molecule. The theory explained by Sidgwick and Powell explain about shape and geometry of the molecule.

The main postulates of VSEPR theory are as follows
*The shape of a molecule depends upon the number of valence shell electron pairs around the central atom.
*Total number of valence shell electron pairs around the central atom is equal to number of lone pairs + number of bond pairs
*Pairs of electrons in the valence shell repel one another since their electron clouds are negatively charged.
*These pairs of electrons tend to occupy such positions in space that minimise repulsion and thus maximise distance between them and achieve minimum repulsion and maximum stability.
*The valence shell is taken as a sphere with the electron pairs localising on the spherical surface at maximum distance from one another.
A multiple bond is treated as if it is a single electron pair and the two or three electron pairs of a multiple bond are treated as a single super pair.
repulsive interaction of electron pairs follows the order
lone pair-lone pair greater than lone pair-bond pair greater than bond pair-bond pair.
Nyholm and Gillespie refine the vsepr model by explaining the important difference between the lone pairs and bonding pairs of electrons. While the lone pairs are localised on the central atom each bonded pair is shared between two atoms. as a result the lone pair electrons in a molecule occupy more space as compared to the bonding pairs of electrons. this results in greater repulsion between lone pairs of electrons as compared to the lone pair and bond pair and bond pair bond pair repulsion.
These repulsions result in deviations from idealized shapes and alterations in bond angles in molecules.


playlist of whole chapter
chemical bonding and molecular structure
   • Chemical Bonding II Class 10 CBSE and ICSE  


Lecture by
Kapil Mahindrakar
B.Tech
ICT Mumbai