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VSEPR (Valence Shell Electron Pair Repulsion) Theory - (Concept)
VSEPR Theory
Valence shell electron-pair repulsion theory (VSEPR theory) enables us to predict the molecular structure, including approximate bond angles around a central atom of a molecule from the estimation of the number of bonds and lone pairs of electrons in its Lewis structure.
The main postulates of VSEPR theory are:
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The actual shape of molecule depends upon the number of electron pairs (bonder or non–bonded) around the central atom.
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The electron pairs tend to repel each other due to their negative charge.
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Electron pairs arrange themselves in such a way that there exists a minimum repulsion between them.
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The valence shell is considered as a sphere with the electron pairs placed at distance.
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A multiple bond is treated as if it is a single electron pair & the electron pairs which constitute the bond as a single pair.
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The repulsive interaction of electron pairs decreases in the order as mentioned below:
Lone pair (lp) – Lone pair (lp) > Lone pair (lp) – Bond pair (bp) > Bond pair (bp) – Bond pair (bp).
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Double bonds cause more repulsion than single bonds, and triple bonds cause more repulsion than a double bond. This repulsion decreases sharply with increasing bond angle between the electron pairs.
Let us understand VSEPR theory using a gaseous BeF2 molecule. The Lewis structure of BeF2 as shown in the figure, there are only two electron pairs around the central beryllium atom. With two bonds and no lone pairs of electrons on the central atom, the bonds are as far apart as possible, and the electrostatic repulsion between these regions of high electron density is reduced to a minimum when they are on opposite sides of the central atom, thus the bond angle is 180°.
The BeF2 molecule adopts a linear structure in which the two bonds are at maximum distance from each other and maintain an angle of 180°.
As given in the table below, two regions of electron density around a central atom in a molecule form a linear geometry, three regions form a trigonal planar geometry, four regions form a tetrahedral geometry, five regions form a trigonal bipyramidal geometry, and six regions form an octahedral geometry.
| Exam | Chapter |
| JEE MAIN | Chemical Bonding and Molecular Structure |
The molecule having smallest bond angle is :
| A. |
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| B. |
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| C. |
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| D. |
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The correct order of bond angles (smallest first ) in $\mathrm{H}_2 \mathrm{~S}, \mathrm{NH}_3, \mathrm{BF}_3$, and $\mathrm{SiH}_4$ is
| A. |
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| B. |
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| C. |
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| D. |
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The type of hybridisation and number of lone pair (s) of electrons of Xe in $\mathrm{XeOF}_4$ respectively, are :
| A. |
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| B. |
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| C. |
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| D. |
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The shape of a molecule is determined by
| A. |
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| B. |
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| C. |
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| D. |
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The reason for the change in bond angle in the different molecules having the same hybridization is given by:
| A. |
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| B. |
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| C. |
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| D. |
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Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :
Assertion A : The H-O-H bond angle in water molecule is 104.5o.
Reason R : The lone pair - lone pair repulsion of electrons is higher than the bond pair -bond pair repulsion.
In the light of the above statements, choose the correct answer from the options given below :
| A. |
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| B. |
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| C. |
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| D. |
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Shape of $\mathrm{Xe} F_4$ molecule is
| A. |
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| B. |
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| C. |
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| D. |
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Based upon VSEPR theory, match the shape (geometry) of the molecules in List-I with the molecules in List - II and select the most appropriate option.
| List-I | List-II |
| (Shape) | (Molecules) |
| (A) T-Shaped | (I)$\mathrm{XeF}_4$ |
| (B) Trigonal planar | (II)$\mathrm{SF}_4$ |
| (C) Square planar | (III)$\mathrm{ClF}_4$ |
| (D) See-Saw | (IV)$\mathrm{BF}_4$ |
| A. |
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| B. |
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| C. |
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| D. |
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Match List - I with List - II.
|
List - I (Compound) |
List- II (Shape) |
| (A) |
(I) bent |
| (B) |
(II) square pyramidal |
| (C) |
(III) trigonal bipyramidal |
| (D) |
(IV) octahedral |
Choose the correct answer from the options given below:
| A. |
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| B. |
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| C. |
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| D. |
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Number of lone pairs of electrons in the central atom of $\mathrm{SCl}_{2^{\prime}} \mathrm{O}_3, \mathrm{ClF}_3$ and SF6 respectively, are:
| A. |
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| B. |
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| C. |
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| D. |
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The number of species having non-pyramidal shape among the following is_______
(A) $\mathrm{SO}_3$
(B) $\mathrm{NO}_3^{-}$
(C) $\mathrm{PCl}_3$
(D) $\mathrm{CO}_3^{2-}$
| A. |
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| B. |
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| C. |
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| D. |
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The sum of number of lone pairs of electrons present on the central atoms of $\mathrm{XeO}_3, \mathrm{XeOF}_4$ and $\mathrm{XeF}_6$, is
| A. |
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| B. |
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| C. |
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| D. |
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The number of molecule(s) or ion(s) from the following having non-planar structure is $\qquad$ $\mathrm{NO}_3^{-}, \mathrm{H}_2 \mathrm{O}_2, \mathrm{BF}_3, \mathrm{PCl}_3, \mathrm{XeF}_4, \mathrm{SF}_4, \mathrm{XeO}_3, \mathrm{PH}_4^{+}, \mathrm{SO}_3,\left[\mathrm{Al}(\mathrm{OH})_4\right]^{-}$
| A. |
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| B. |
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| C. |
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| D. |
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The number of interhalogens from the following having square pyramidal structure is :
| A. |
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| B. |
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| C. |
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| D. |
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Which one of the following is the correct bond angle between atoms adopting a trigonal planar geometry ____°
| A. |
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| B. |
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| C. |
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| D. |
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The number of species from the following in which the central atom uses $\mathrm{sp}^3$ hybrid orbitals in its bonding is_______.
$\mathrm{NH}_3, \mathrm{SO}_2, \mathrm{SiO}_2, \mathrm{BeCl}_2, \mathrm{CO}_2, \mathrm{H}_2 \mathrm{O}, \mathrm{CH}_4, \mathrm{BF}_3$
| A. |
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| B. |
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| C. |
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| D. |
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The correct order of repulsive interaction of electron pair :-
| A. |
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| B. |
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| C. |
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| D. |
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The shape of the XeO2F2 molecule is
| A. |
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| B. |
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| C. |
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| D. |
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Which of the following properties does not explain VBT
| A. |
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| B. |
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| C. |
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| D. |
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What is the shape of SF4 molecule
| A. |
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| B. |
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| C. |
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| D. |
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what is the shape of NH4+
| A. |
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| B. |
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| C. |
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| D. |
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Directions: In the following questions, a statement if Assertion (A) is followed by a statement of reason (R).
Assertion: Shape of XeF4 molecule is square planar.
Reason: The lone pairs are present at 1800 to each other to minimize the repulsion.
Mark the correct choice as:
| A. |
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| B. |
|
| C. |
|
| D. |
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Complexes $\left(M L_5\right)$ of metals $N i$ and $F e$ have ideal square pyramidal and trigonal bipyramidal geometries, respectively. The sum of the $90^{\circ}, 120^{\circ}$ and $180^{\circ} L-M-L$ angles in the two complexes is _________.
| A. |
|
| B. |
|
| C. |
|
| D. |
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Total number of lone pair in SO3 is
| A. |
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| B. |
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| C. |
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| D. |
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Incorrectly matched pair is :
| A. |
|
| B. |
|
| C. |
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| D. |
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Which of the following statement is true for $\left[I O_2 F_2\right]^{-}$according to VSEPR theory?
| A. |
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| B. |
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| C. |
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| D. |
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The numbers of lone pair(s) on Xe in $\mathrm{XeF}_2$ and $\mathrm{XeF}_4$ are, respectively,
| A. |
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| B. |
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| C. |
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| D. |
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A central atom in a molecule has two lone pairs of electrons and forms three single bonds. The shape of this molecule is :
| A. |
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| B. |
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| C. |
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| D. |
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Amongst $\mathrm{SF}_4, \mathrm{XeF}_4, \mathrm{CF}_4$ and $\mathrm{H}_2 \mathrm{O}$, the number of species with two lone pairs of electrons on central atom is __________________________
| A. |
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| B. |
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| C. |
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| D. |
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In $B r F_3$ molecule,the lone pairs occupy equatorial positions to minimize
| A. |
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| B. |
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| C. |
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| D. |
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In $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$
| A. |
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| B. |
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| C. |
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| D. |
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The correct increasing order for bond angles among $\mathrm{BF}_3, \mathrm{PF}_3$ and $\mathrm{C} \ell \mathrm{F}_3$ is :
| A. |
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| B. |
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| C. |
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| D. |
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$$
\text { The decreasing order of bond angles in } \mathrm{BF}_3, \mathrm{NH}_3, \mathrm{PF}_3 \text { and } I_3^{-} \text {is: }
$$
| A. |
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| B. |
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| C. |
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| D. |
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Two statements are given in the following question one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these question from the codes (i), (ii), (iii) and (iv) as given below:
Assertion (A): The $C-O-H$ bond angle in alcohols is slightly less than the tetrahedral angle.
Reason (R): This is due to the repulsive interaction between the two lone electron pairs on oxygen.
| A. |
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| B. |
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| C. |
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| D. |
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The HCH bond angle in HCHO is nearly equal to ____o
| A. |
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| B. |
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| C. |
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| D. |
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The hybridisation and geometry of SO42- respectively are:
| A. |
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| B. |
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| C. |
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| D. |
|
$$
\text { The hybridisation of orbitals of } \mathrm{N} \text { atom in } \mathrm{NO}_3^{-}, \mathrm{NO}_2^{+} \text {and } \mathrm{NH}_4^{+} \text {are respectively }
$$
| A. |
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| B. |
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| C. |
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| D. |
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The hybridisation of P in red phosphorus is -
| A. |
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| B. |
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| C. |
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| D. |
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The Hybridisation of PCl5 in solid state -
| A. |
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| B. |
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| C. |
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| D. |
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$\text { The hybridisation of } \mathrm{IF}_7 \text { is }$
| A. |
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| B. |
|
| C. |
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| D. |
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Which of the following is not tetrahedral in shape?
| A. |
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| B. |
|
| C. |
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| D. |
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The structure of $\mathrm{XeOF}_4$ is
| A. |
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| B. |
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| C. |
|
| D. |
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A molecule with the formula AX4Y has all it’s elements from p-block. Element A is rarest,
monoatomic, non-radioactive from its group and has the lowest ionization enthalpy value among A, X and Y. Elements X and Y have first and second highest electronegativity values respectively among all the known elements. The shape of the molecule is :
| A. |
|
| B. |
|
| C. |
|
| D. |
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Which among the following molecules is (a) involved in sp3d hybridization, (b) has different bond lengths and (c) has lone pair of electrons on the central atom ?
| A. |
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| B. |
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| C. |
|
| D. |
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As already explained, Lewis concept is unable to explain the shapes of molecules. This theory provides a simple procedure to predict the shapes 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.
