give postulates of VSEPR THEORY
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these are the postulates of VSEPR theory
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Answer :
❀ Main postulates of Valence Shell Electron Pair Repulsion (VSEPR) Theory are :-
✏ The shape of a molecule depends upon the number of valence shell electron pairs (bonded or non - bonded) around the central atom.
✏ Pairs of electrons in the valence shell repel one another since 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.
✏ 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.
✏ When two or more resonance structures can represent a molecule, the VSEPR model is applicable to any such structure.
★ Supplementary Counsel :-
• The repulsive interaction of electron pairs decrease in the order : Lone pair (lp) ñ Lone pair (lp) > Lone pair (lp) ñ
Lone pair (lp) > Lone pair (lp) ñ Bond Pair (bp) > Bond pair (bp) ñ Bond Pair (bp)
• This theory provides a simple procedure to predict the shape of covalent molecules.
• Sidgwick and Powell in 1940, proposed a simple theory based on the repulsion interactions of the electron pairs in the valence shell of the atoms.
• It was further developed and redefined by Nyholm and Gillespie (1957)
• While the lone pairs are localised on the central atom, each bonded pair is shared between the atoms.