Chemical Bonding in NEET: Important Theories & Questions

Introduction

Chemical bonding is a cornerstone of NEET Chemistry preparation. It acts as the foundational pillar that interlinks various chapters—ranging from the molecular structures in Organic Chemistry to reaction mechanisms in Coordination Compounds and the periodic behavior of elements. This topic explains how atoms combine to form compounds and how the nature of chemical bonds affects the properties and reactivities of substances.

For NEET aspirants aiming to score high in Chemistry, this chapter isn’t just important—it’s essential. Understanding concepts like hybridization, molecular geometry, resonance, bond order, and magnetism not only helps in solving direct questions but also aids comprehension in subsequent chapters. In this detailed guide from Deeksha Vedantu, we present a comprehensive breakdown of chemical bonding theories, smart memorization tricks, tables for quick recall, and NEET-level practice questions that will strengthen your preparation.

Weightage of Chemical Bonding in NEET

Chemical bonding typically contributes around 2 to 3 questions in the NEET Chemistry paper each year. Although this may seem like a small portion, these questions are often direct and can be solved quickly if you understand the core principles.

Common topics asked in NEET:

Identifying hybridization and predicting molecular shape
Determining magnetic nature using MOT
Calculating bond order for given molecules
Geometry and electron pair arrangement (VSEPR-based)
Drawing Lewis structures and understanding resonance

These questions test your conceptual clarity more than rote memorization. Hence, mastering them is a sure-shot way to secure marks.

Key Theories in Chemical Bonding

Lewis Structures & Octet Rule

Lewis dot structures represent the valence electrons in molecules and help predict how atoms bond and share electrons. Most atoms follow the Octet Rule, where they try to achieve 8 electrons in their outermost shell.

Types of Exceptions:

Incomplete octet: Molecules like $\boldsymbol{\text{BF}_3}$ and $\boldsymbol{\text{BeCl}_2}$ have central atoms with fewer than 8 electrons.
Expanded octet: Atoms like phosphorus and sulfur in $\boldsymbol{\text{PCl}_5}$ , $\boldsymbol{\text{SF}_6}$ accommodate more than 8 electrons.
Odd-electron species: Molecules such as $\boldsymbol{\text{NO}}$ and $\boldsymbol{\text{NO}_2}$ have unpaired electrons and do not satisfy the octet.

Drawing Lewis structures correctly is a prerequisite for VSEPR theory, hybridization, and understanding resonance.

Valence Bond Theory (VBT)

Valence Bond Theory suggests that bonds are formed due to the overlap of atomic orbitals. It explains:

Sigma $\boldsymbol{(\sigma)}$ bonds: Formed via head-on overlap
Pi $\boldsymbol{(\pi)}$ bonds: Formed by sideways overlap

Hybridization is a central aspect of VBT, involving the mixing of orbitals to form new hybrid orbitals

Hybridization	Orbitals Mixed	Geometry	Bond Angle	Example
$\boldsymbol{sp^3}$	1 s + 3 p	Tetrahedral	$\boldsymbol{\sim 109.5^\circ}$	$\boldsymbol{\text{CH}_4}$
$\boldsymbol{sp^2}$	1 s + 2 p	Trigonal planar	$\boldsymbol{\sim 120^\circ}$	$\boldsymbol{\text{BF}_3}$
$\boldsymbol{sp}$	1 s + 1 p	Linear	$\boldsymbol{\sim 180^\circ}$	$\boldsymbol{\text{BeCl}_2}$
$\boldsymbol{sp^3d}$	1 s + 3 p + 1 d	Trigonal bipyramidal	$\boldsymbol{90^\circ, 120^\circ}$	$\boldsymbol{\text{PCl}_5}$
$\boldsymbol{sp^3d^2}$	1 s + 3 p + 2 d	Octahedral	$\boldsymbol{90^\circ}$	$\boldsymbol{\text{SF}_6}$

Limitations: VBT fails to explain certain properties like magnetism and relative bond energies, which are better explained by Molecular Orbital Theory.

Molecular Orbital Theory (MOT)

MOT describes chemical bonding as the combination of atomic orbitals to form molecular orbitals that extend over the entire molecule.

Types of Orbitals:

Bonding orbitals: Stabilize the molecule (lower energy)
Antibonding orbitals: Destabilize the molecule (higher energy, denoted as *)

Bond Order Formula: Bond Order = (Number of bonding electrons – Number of antibonding electrons) / 2

Examples:

$\boldsymbol{\text{O}_2}$ : Bond order = $\boldsymbol{2}$ , paramagnetic (due to unpaired electrons)
$\boldsymbol{\text{N}_2}$ : Bond order = $\boldsymbol{3}$ , diamagnetic
$\boldsymbol{\text{O}_2^-}$ : Bond order = $\boldsymbol{1.5}$ , weaker bond than $\boldsymbol{\text{O}_2}$

MO Configuration Tips:

For $\boldsymbol{\text{B}_2}$ , $\boldsymbol{\text{C}_2}$ , $\boldsymbol{\text{N}_2}$ : $\boldsymbol{\sigma(2p_z) < \pi(2p_x) = \pi(2p_y)}$
For $\boldsymbol{\text{O}_2}$ , $\boldsymbol{\text{F}_2}$ : $\boldsymbol{\pi(2p_x) = \pi(2p_y) < \sigma(2p_z)}$

Understanding these configurations is crucial to determining magnetic behavior and bond strength.

VSEPR Theory

The Valence Shell Electron Pair Repulsion theory predicts the 3D shape of molecules based on the repulsion between lone pairs and bond pairs of electrons.

AXE Method:

A: Central atom
X: Bonded atoms
E: Lone pairs

Geometry Guide:

AXE Formula	Shape	Example	Hybridization
$\boldsymbol{\text{AX}_2}$	Linear	$\boldsymbol{\text{BeCl}_2}$	$\boldsymbol{sp}$
$\boldsymbol{\text{AX}_3}$	Trigonal Planar	$\boldsymbol{\text{BF}_3}$	$\boldsymbol{sp^2}$
$\boldsymbol{\text{AX}_2\text{E}}$	Bent	$\boldsymbol{\text{SO}_2}$	$\boldsymbol{sp^2}$
$\boldsymbol{\text{AX}_4}$	Tetrahedral	$\boldsymbol{\text{CH}_4}$	$\boldsymbol{sp^3}$
$\boldsymbol{\text{AX}_3\text{E}}$	Trigonal Pyramidal	$\boldsymbol{\text{NH}_3}$	$\boldsymbol{sp^3}$
$\boldsymbol{\text{AX}_2\text{E}_2}$	Bent	$\boldsymbol{\text{H}_2\text{O}}$	$\boldsymbol{sp^3}$
$\boldsymbol{\text{AX}_5}$	Trigonal Bipyramidal	$\boldsymbol{\text{PCl}_5}$	$\boldsymbol{sp^3d}$
$\boldsymbol{\text{AX}_4\text{E}}$	Seesaw	$\boldsymbol{\text{SF}_4}$	$\boldsymbol{sp^3d}$
$\boldsymbol{\text{AX}_4\text{E}_2}$	Square Planar	$\boldsymbol{\text{XeF}_4}$	$\boldsymbol{sp^3d^2}$

Key Insight: Lone pairs occupy more space than bonding pairs, causing distortions in shape and reducing bond angles.

Coordinate Bonds & Resonance

Coordinate Bonds involve the donation of a lone pair by one atom to another that lacks electrons. Common in ions like NH₄⁺, where nitrogen donates a lone pair to a proton.

Resonance Structures arise when more than one valid Lewis structure exists. The actual structure is a hybrid of all contributing forms.

Examples:

Ozone $\boldsymbol{\text{(O}_3\text{)}}$ has delocalized double bonds
Nitrate ion $\boldsymbol{\text{(NO}_3^-\text{)}}$ exhibits symmetrical resonance
Benzene $\boldsymbol{\text{(C}_6\text{H}_6\text{)}}$ shows equal bond lengths due to resonance stabilization

Resonance contributes to bond stability, lowers energy, and enhances molecular symmetry.

Hybridization Chart: Quick Reference Table

Molecule	Central Atom	Hybridization	Geometry	Bond Angle
$\boldsymbol{\text{CH}_4}$	C	$\boldsymbol{sp^3}$	Tetrahedral	$\boldsymbol{109.5^\circ}$
$\boldsymbol{\text{NH}_3}$	N	$\boldsymbol{sp^3}$	Trigonal Pyramidal	$\boldsymbol{\sim 107^\circ}$
$\boldsymbol{\text{H}_2\text{O}}$	O	$\boldsymbol{sp^3}$	Bent	$\boldsymbol{\sim 104.5^\circ}$
$\boldsymbol{\text{BF}_3}$	B	$\boldsymbol{sp^2}$	Trigonal Planar	$\boldsymbol{120^\circ}$
$\boldsymbol{\text{BeCl}_2}$	Be	$\boldsymbol{sp}$	Linear	$\boldsymbol{180^\circ}$
$\boldsymbol{\text{SF}_6}$	S	$\boldsymbol{sp^3d^2}$	Octahedral	$\boldsymbol{90^\circ}$
$\boldsymbol{\text{XeF}_4}$	Xe	$\boldsymbol{sp^3d^2}$	Square Planar	$\boldsymbol{90^\circ}$

Use the steric number = (Number of bonded atoms + lone pairs) to determine hybridization quickly.

Bond Order, Length, and Energy

Understanding bond order helps predict the strength, length, and stability of a bond:

Higher bond order = Stronger bond = Shorter length
Lower bond order = Weaker bond = Longer length

Trends:

$\boldsymbol{\text{N}_2}$ : Bond order = $\boldsymbol{3}$ → Strong triple bond
$\boldsymbol{\text{O}_2}$ : Bond order = $\boldsymbol{2}$ → Moderate double bond
$\boldsymbol{\text{F}_2}$ : Bond order = $\boldsymbol{1}$ → Weak single bond
$\boldsymbol{\text{O}_2^-}$ : Bond order = $\boldsymbol{1.5}$ → Longer and weaker than $\boldsymbol{\text{O}_2}$

Application in NEET: Questions may ask for comparative bond lengths, strengths, or require you to calculate bond order from MO diagrams.

Practice Questions with Concepts

What is the hybridization and shape of $\boldsymbol{\text{SF}_4}$ and $\boldsymbol{\text{SF}_6}$ ?
Identify the paramagnetic species: $\boldsymbol{\text{O}_2}$ , $\boldsymbol{\text{N}_2}$ , $\boldsymbol{\text{F}_2}$ , $\boldsymbol{\text{O}_2^-}$
Calculate the bond order of $\boldsymbol{\text{CN}^-}$ , $\boldsymbol{\text{NO}^+}$ , and $\boldsymbol{\text{O}_2^+}$
Predict molecular geometry using VSEPR: $\boldsymbol{\text{ClF}_3}$ , $\boldsymbol{\text{XeF}_2}$ , $\boldsymbol{\text{IF}_5}$
Match species with their hybridization: $\boldsymbol{\text{NH}_3}$ , $\boldsymbol{\text{PCl}_5}$ , $\boldsymbol{\text{CH}_4}$ , $\boldsymbol{\text{BF}_3}$

Common Mistakes to Avoid

Confusing geometry with shape (e.g., NH₃ has a tetrahedral geometry but a trigonal pyramidal shape)
Skipping lone pairs in AXE method, leading to incorrect shape predictions
Applying wrong MO configurations beyond O₂ molecule
Forgetting exceptions to octet rule for elements in period 2 vs period 3
Misinterpreting coordinate bonds as always polar—they may not be, depending on molecular symmetry

FAQs

Is hybridization still relevant for NEET 2025?

Yes. NEET continues to include questions on hybridization, bond angles, and molecular shape.

Should I memorize molecular orbital diagrams?

Yes. Especially from B₂ to Ne₂. Focus more on O₂ and N₂, which appear frequently in NEET.

Which bonding theory should I use for what type of question?

VBT for hybridization and sigma/pi bonds
MOT for bond order, magnetism
VSEPR for shape and geometry

What is the easiest way to remember hybridization?

Use the steric number (bonded atoms + lone pairs) to determine hybridization. A steric number of 4 indicates sp³, 3 means sp², and 2 means sp.

Why do some molecules have distorted shapes even with similar hybridization?

Distortion often arises due to lone pairs. They occupy more space than bonding pairs and push bonded atoms closer together, altering the ideal bond angle.

Are all resonance structures equally stable?

No. Structures with complete octets, minimal formal charges, and electronegative atoms bearing negative charges are generally more stable.

Do coordinate bonds affect molecular shape?

Coordinate bonds are treated like normal covalent bonds in shape predictions using VSEPR theory, so they do not affect geometry differently.

Can a molecule exhibit more than one type of hybridization?

Yes. In complex molecules, different atoms or even the same central atom (in different resonance forms or states) may show varying hybridization.

How can I quickly identify bond order in polyatomic ions?

Use Lewis structures and consider resonance. Divide the total number of bonds by the number of bonding positions between the same atoms (e.g., in NO₃⁻: 4 bonds/3 positions = bond order 1.33).

Is understanding resonance important for Organic Chemistry?

Absolutely. Resonance helps explain the stability, reactivity, and acidity/basicity of organic molecules.

Conclusion

Chemical Bonding is one of the most scoring and concept-driven topics in NEET Chemistry. Mastering bonding theories like Lewis Structures, VBT, MOT, and VSEPR improves clarity not only for standalone questions but also enhances understanding in Organic, Inorganic, and Physical Chemistry.

At Deeksha Vedantu, we help NEET aspirants strengthen their bonding concepts through clear visual aids, conceptual mind maps, and theory-to-practice integration. By using structured notes, smart shortcuts, and targeted practice, you can master Chemical Bonding in a systematic and stress-free way.

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Introduction
Weightage of Chemical Bonding in NEET
Key Theories in Chemical Bonding
Hybridization Chart: Quick Reference Table
Bond Order, Length, and Energy
Practice Questions with Concepts
Common Mistakes to Avoid
FAQs
Conclusion