Chemical Bonding and Molecular Structure

Class 11

19 previous-year questions from this chapter every option and the correct answer, free · where the marks are

1. Ionic and covalent bonds, Lewis structures

Exam focus: Fajans' rules explain why some "ionic" compounds behave covalently: a small, highly charged cation next to a large, polarisable anion pulls electron density back toward itself, which is why AlCl₃ and BeCl₂ don't act like typical ionic solids. Octet exceptions — BF₃ incomplete, PCl₅/SF₆ expanded, NO odd-electron — are tested directly, not as a footnote.

Chemical Bonding and Molecular Structure — Full Chapter

Vedantu 11&12

Full-chapter one-shot; ionic/covalent bonds and Lewis structures are covered as the opening section.

2. VSEPR and molecular shapes

Exam focus: Shape isn't the same as electron-pair geometry: NH₃ and H₂O both have a tetrahedral arrangement of electron pairs, but lone pairs are dropped when naming the shape (pyramidal, bent). The repulsion order lone pair–lone pair > lone pair–bond pair > bond pair–bond pair is why NH₃'s bond angle (107°, one lone pair) is squeezed less than H₂O's (104.5°, two lone pairs).

Chemical Bonding and Molecular Structure — Full Chapter

Vedantu 11&12

Same full-chapter video; VSEPR theory and molecular shapes are one section of it.

ChemistryNEET 2025show ▾

Identify the correct orders against the property mentioned: A.

H_{2} O > N H_{3} > CHC l_{3}

— dipole moment B.

Xe F_{4} > Xe O_{3} > Xe F_{2}

— number of lone pairs on the central atom C. O–H > C–H > N–O — bond length D.

N_{2} > O_{2} > H_{2}

— bond enthalpy Choose the correct answer from the options given below:

A.A, D only✓
B.B, D only
C.A, C only
D.B, C only

Solution

Dipole moments: $H_{2} O$ (1.85 D) > $N H_{3}$ (1.47 D) > $CHC l_{3}$ (1.04 D) — A correct. Bond enthalpy: N≡N (945) > O=O (498) > H–H (436 kJ/mol) — D correct. $Xe F_{2}$ has three lone pairs on Xe, more than $Xe F_{4}$ 's two — B wrong. Bond lengths run N–O (~140 pm) > C–H (109 pm) > O–H (96 pm), the reverse of C — C wrong. Hence A and D.

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ChemistryNEET 2024show ▾

Match List I with List II.

List I (Compound)	List II (Shape/geometry)
A. $N H_{3}$	I. Trigonal pyramidal
B. $Br F_{5}$	II. Square planar
C. $Xe F_{4}$	III. Octahedral
D. $S F_{6}$	IV. Square pyramidal

Choose the correct answer from the options given below:

A.A-II, B-IV, C-III, D-I
B.A-III, B-IV, C-I, D-II
C.A-II, B-III, C-IV, D-I
D.A-I, B-IV, C-II, D-III✓

Solution

$N H_{3}$ : $s p^{3}$ with one lone pair — trigonal pyramidal (I). $Br F_{5}$ : $s p^{3} d^{2}$ with one lone pair — square pyramidal (IV). $Xe F_{4}$ : $s p^{3} d^{2}$ with two lone pairs — square planar (II). $S F_{6}$ : octahedral (III).

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ChemistryNEET 2022show ▾

Amongst the following, which one will have maximum 'lone pair – lone pair' electron repulsions?

A. $Xe F_{2}$ ✓
B. $Cl F_{3}$
C. $I F_{5}$
D. $S F_{4}$

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ChemistryNEET 2021show ▾

Match List-I with List-II.

List-I	List-II
(a) $PC l_{5}$	(i) Square pyramidal
(b) $S F_{6}$	(ii) Trigonal planar
(c) $Br F_{5}$	(iii) Octahedral
(d) $B F_{3}$	(iv) Trigonal bipyramidal

Choose the correct answer from the options given below:

A.(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)✓
B.(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
C.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
D.(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

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ChemistryNEET 2019show ▾

Identify the incorrect statement related to

PC l_{5}

from the following:

A.The three equatorial P–Cl bonds make an angle of $12 0^{\circ}$ with each other
B.The two axial P–Cl bonds make an angle of $18 0^{\circ}$ with each other
C.Axial P–Cl bonds are longer than equatorial P–Cl bonds
D. $PC l_{5}$ molecule is non-reactive✓

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3. Valence bond theory and hybridisation

Exam focus: Hybridisation is decided by the steric number — sigma bonds plus lone pairs on the central atom — not by the number of bonds alone; forgetting a lone pair is the most common way to misassign sp³ to something that's actually sp³d or sp³d² (XeF₄ is sp³d², with two lone pairs on Xe alongside its four bonds).

Chemical Bonding and Molecular Structure — Full Chapter

Vedantu 11&12

Same full-chapter video; valence bond theory and hybridisation are covered within it.

4. Molecular orbital theory

Exam focus: MOT's headline NEET question is O₂'s paramagnetism — two unpaired electrons in its degenerate π*2p orbitals, which the paired-electron double-bond picture from Lewis structures or VBT can't show at all. Watch the filling order too: from Li₂ to N₂, σ2p fills after π2p (s–p mixing pushes it up); from O₂ onward σ2p drops back below π2p.

Chemical Bonding and Molecular Structure — Full Chapter

Vedantu 11&12

Same full-chapter video; molecular orbital theory is one section of this one-shot.

ChemistryNEET 2025show ▾

Given below are two statements: Statement I: A hypothetical diatomic molecule with bond order zero is quite stable. Statement II: As bond order increases, the bond length increases. In the light of the above statements, choose the most appropriate answer from the options given below:

A.Both Statement I and Statement II are true
B.Both Statement I and Statement II are false✓
C.Statement I is true but Statement II is false
D.Statement I is false but Statement II is true

Solution

Bond order zero means no net bonding — the molecule does not form (I false). Higher bond order means a shorter, stronger bond, so bond length decreases (II false).

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ChemistryNEET 2024show ▾

Match List I with List II.

List I (Molecule)	List II (Number and type of bonds between two carbon atoms)
A. ethane	I. one $σ -$ bond and two $π -$ bonds
B. ethene	II. two $π -$ bonds
C. carbon molecule, $C_{2}$	III. one $σ -$ bond
D. ethyne	IV. one $σ -$ bond and one $π -$ bond

Choose the correct answer from the options given below:

A.A-IV, B-III, C-II, D-I
B.A-III, B-IV, C-II, D-I✓
C.A-III, B-IV, C-I, D-II
D.A-I, B-IV, C-II, D-III

Solution

Ethane: one C– $C σ$ bond (III). Ethene: one $σ$ and one $π ($ IV). Ethyne: one $σ$ and two $π (I)$ . By molecular orbital theory the $C_{2}$ molecule has a double bond made of two $π$ bonds only (II). Hence A-III, B-IV, C-II, D-I.

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ChemistryNEET 2023show ▾

The correct order of energies of the molecular orbitals of the

N_{2}

molecule is:

A. $σ 1 s < σ^{*} 1 s < σ 2 s < σ^{*} 2 s < (π 2 p_{x} = π 2 p_{y}) < σ 2 p_{z} < (π^{*} 2 p_{x} = π^{*} 2 p_{y}) < σ^{*} 2 p_{z}$ ✓
B. $σ 1 s < σ^{*} 1 s < σ 2 s < σ^{*} 2 s < σ 2 p_{z} < (π 2 p_{x} = π 2 p_{y}) < (π^{*} 2 p_{x} = π^{*} 2 p_{y}) < σ^{*} 2 p_{z}$
C. $σ 1 s < σ^{*} 1 s < σ 2 s < σ^{*} 2 s < σ 2 p_{z} < σ^{*} 2 p_{z} < (π 2 p_{x} = π 2 p_{y}) < (π^{*} 2 p_{x} = π^{*} 2 p_{y})$
D. $σ 1 s < σ^{*} 1 s < σ 2 s < σ^{*} 2 s < (π 2 p_{x} = π 2 p_{y}) < (π^{*} 2 p_{x} = π^{*} 2 p_{y}) < σ 2 p_{z} < σ^{*} 2 p_{z}$

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ChemistryNEET 2022show ▾

Which amongst the following is an incorrect statement?

A. $O_{2}^{+}$ ion is diamagnetic✓
B.The bond orders of $O_{2}^{+}$ , $O_{2}$ , $O_{2}^{-}$ and $O_{2}^{2 -}$ are 2.5, 2, 1.5 and 1, respectively
C.The $C_{2}$ molecule has four electrons in its two degenerate $π$ molecular orbitals
D. $H_{2}^{+}$ ion has one electron

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ChemistryNEET 2020show ▾

Identify a molecule which does not exist.

A. $H e_{2}$ ✓
B. $L i_{2}$
C. $C_{2}$
D. $O_{2}$

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ChemistryNEET 2019show ▾

Which of the following diatomic molecular species has only

σ

bonds according to Molecular Orbital Theory?

A. $O_{2}$
B. $N_{2}$
C. $C_{2}$ ✓
D. $B e_{2}$

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5. Hydrogen bonding and dipole moment

Exam focus: Net dipole moment is a vector sum of bond dipoles, not a scalar one — CO₂'s two C=O dipoles cancel exactly in its linear geometry (μ=0), while bent H₂O's don't. The classic trap: o-nitrophenol's intramolecular hydrogen bond makes it more volatile than p-nitrophenol, whose hydrogen bonding is intermolecular — having H-bonds isn't enough, the question is whether they're within or between molecules.

Chemical Bonding and Molecular Structure — Full Chapter

Vedantu 11&12

Same full-chapter video; hydrogen bonding and dipole moment are covered near the end of this one-shot.

ChemistryNEET 2024show ▾

Identify the correct answer.

A. $B F_{3}$ has a non-zero dipole moment
B.The dipole moment of $N F_{3}$ is greater than that of $N H_{3}$
C.Three canonical forms can be drawn for the $C O_{3}^{2 -}$ ion✓
D.Three resonance structures can be drawn for ozone

Solution

$C O_{3}^{2 -}$ has three equivalent resonance structures with the double bond on each oxygen in turn. $B F_{3}$ is trigonal planar with zero dipole; $N H_{3}$ has a larger dipole than $N F_{3}$ ; ozone has two resonance structures.

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ChemistryNEET 2024show ▾

Intramolecular hydrogen bonding is present in (three options drawn as structures; the third is HF): Question 68 as printed in the NEET 2024 booklet

Question 68 as printed in the NEET 2024 booklet

A.Structure (1)
B.Structure (2)
C.HF
D.Structure (4)✓

Solution

Only in o-nitrophenol are the –OH and –NO $_{2}$ groups close enough to form a hydrogen bond within the same molecule (a six-membered chelate ring). The m- and p-isomers and HF hydrogen-bond only between molecules.

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ChemistryNEET 2023show ▾

Intermolecular forces are forces of attraction and repulsion between interacting particles that will include: A. dipole–dipole forces B. dipole–induced dipole forces C. hydrogen bonding D. covalent bonding E. dispersion forces Choose the most appropriate answer from the options given below:

A.B, C, D, E are correct
B.A, B, C, D are correct
C.A, B, C, E are correct✓
D.A, C, D, E are correct

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ChemistryNEET 2022show ▾

Given below are two statements: Statement I: The boiling points of the following hydrides of group 16 elements increase in the order

H_{2} O < H_{2} S < H_{2} Se < H_{2} Te

. Statement II: The boiling points of these hydrides increase with increase in molar mass. In the light of the above statements, choose the most appropriate answer from the options given below:

A.Statement I is incorrect but Statement II is correct
B.Both Statement I and Statement II are correct
C.Both Statement I and Statement II are incorrect✓
D.Statement I is correct but Statement II is incorrect

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ChemistryNEET 2021show ▾

Which of the following molecules is non-polar in nature?

A. $POC l_{3}$
B. $C H_{2} O$
C. $SbC l_{5}$ ✓
D. $N O_{2}$

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ChemistryNEET 2020show ▾

Which of the following sets of molecules will have zero dipole moment?

A.Ammonia, beryllium difluoride, water, 1,4-dichlorobenzene
B.Boron trifluoride, hydrogen fluoride, carbon dioxide, 1,3-dichlorobenzene
C.Nitrogen trifluoride, beryllium difluoride, water, 1,3-dichlorobenzene
D.Boron trifluoride, beryllium difluoride, carbon dioxide, 1,4-dichlorobenzene✓

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