Write the limitations of the Lewis concept and the main postulates of $VSEPR$ theory.
Limitations of Lewis concept: The Lewis concept is unable to explain the shapes of molecules.
Valence Shell Electron Pair Repulsion $(VSEPR)$ theory: 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 repulsive interactions of the electron pairs in the valence shell of the atoms.
Postulates of $VSEPR$ Theory:
- 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 their electron clouds are negatively charged.
- These pairs of electrons tend to occupy such positions in space that minimize repulsion and thus maximize the distance between them.
- The valence shell is taken as a sphere with the electron pairs localizing 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.
- Where two or more resonance structures can represent a molecule,the $VSEPR$ model is applicable to any such structure.
- The repulsive interaction of electron pairs decreases in the order: $[Lone \ pair \ (lp) - Lone \ pair \ (lp)] > [Lone \ pair \ (lp) - Bond \ pair \ (bp)] > [Bond \ pair \ (bp) - Bond \ pair \ (bp)]$
Valence Shell Electron Pair Repulsion $(VSEPR)$ theory: 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 repulsive interactions of the electron pairs in the valence shell of the atoms.
Postulates of $VSEPR$ Theory:
- 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 their electron clouds are negatively charged.
- These pairs of electrons tend to occupy such positions in space that minimize repulsion and thus maximize the distance between them.
- The valence shell is taken as a sphere with the electron pairs localizing 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.
- Where two or more resonance structures can represent a molecule,the $VSEPR$ model is applicable to any such structure.
- The repulsive interaction of electron pairs decreases in the order: $[Lone \ pair \ (lp) - Lone \ pair \ (lp)] > [Lone \ pair \ (lp) - Bond \ pair \ (bp)] > [Bond \ pair \ (bp) - Bond \ pair \ (bp)]$
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Similar Questions
Select the incorrect match regarding molecular geometry:
Statement $-$ Shape $-$ Example
$A$. $SF_4$ $-$ See-saw $-$ $SF_4$
$B$. $BrF_3$ $-$ $T$-shaped $-$ $BrF_3$
$C$. $XeF_4$ $-$ Square planar $-$ $XeF_4$
$D$. $ICl_2^-$ $-$ Linear $-$ $ICl_2^-$
Statement $-$ Shape $-$ Example
$A$. $SF_4$ $-$ See-saw $-$ $SF_4$
$B$. $BrF_3$ $-$ $T$-shaped $-$ $BrF_3$
$C$. $XeF_4$ $-$ Square planar $-$ $XeF_4$
$D$. $ICl_2^-$ $-$ Linear $-$ $ICl_2^-$
The shape of $XeF_{5}^{-}$ will be
Given below are two statements:
Statement $I$: The number of compounds among $SO_2$, $SO_3$, $SF_4$, $SF_6$ and $H_2S$ in which sulphur does not obey the Octet rule is $3$.
Statement $II$: Among $[H_2O, ClF_3, SF_4]$, $[NH_3, BrF_5, SF_4]$, $[BrF_5, ClF_3, XeF_4]$ and $[XeF_4, ClF_3, H_2O]$, the number of sets in which all the molecules have one lone pair of electrons on the central atom is $1$.
Statement $I$: The number of compounds among $SO_2$, $SO_3$, $SF_4$, $SF_6$ and $H_2S$ in which sulphur does not obey the Octet rule is $3$.
Statement $II$: Among $[H_2O, ClF_3, SF_4]$, $[NH_3, BrF_5, SF_4]$, $[BrF_5, ClF_3, XeF_4]$ and $[XeF_4, ClF_3, H_2O]$, the number of sets in which all the molecules have one lone pair of electrons on the central atom is $1$.
DifficultJEE MAIN 2026
View SolutionIn which of the following options,the molecules are correctly arranged in the increasing order of their bond angles?
The atomic number of $Sn$ is $50$. The shape of gaseous $SnCl_{2}$ molecule is
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