Chapter 13 of 25

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Tamil Nadu (TNBSE)Class 9 Science★ 4-5 marks in assessments

Chemical Bonding

Samacheer Kalvi (TN State Board) Class 9 Science — Chemistry Chapter 13, Chemical Bonding. Chemical bonding explains how atoms link to form molecules. Understanding ionic, covalent, and coordinate bonds explains why some substances melt easily while others are hard, conduct electricity, or dissolve in water. Notes, worked examples, common mistakes, and quick revision.

⏱ 19 min readMedium difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1Explain the octet rule and stability of atoms
2Describe the formation of ionic (electrovalent) bonds with examples
3Describe the formation of covalent bonds with Lewis structures
4Differentiate ionic and covalent compounds

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Why this chapter matters

Chemical bonding explains how atoms link to form molecules. Understanding ionic, covalent, and coordinate bonds explains why some substances melt easily while others are hard, conduct electricity, or dissolve in water.

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Class 9 Science — Atomic Structure

Valency and electron configuration.

Chemical Bonding — Class 9 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 9 Science, Chemistry — Chapter 13. Chemical bonding explains how atoms link to form molecules. Understanding ionic, covalent, and coordinate bonds explains why some substances melt easily while others are hard, conduct electricity, or dissolve in water.

1. About this chapter

This chapter covers octet rule, ionic bonding, covalent bonding, coordinate bonding, and compound properties.

2. Octet Rule and Ionic Bond

Octet Rule: Atoms combine to have 8 valence electrons.
Ionic (Electrovalent) Bond: Formed by transfer of electrons from a metal (gives cation) to a non-metal (gives anion). Example: NaCl, MgO.
Properties of Ionic Compounds: Crystalline solids, high melting/boiling points, soluble in water, conduct electricity in molten or aqueous state.

3. Covalent Bond

Covalent Bond: Formed by mutual sharing of electron pairs between non-metal atoms. Example: H₂, O₂, N₂, H₂O.
Properties of Covalent Compounds: Liquids or gases (mostly), low melting/boiling points, insoluble in water (soluble in organic solvents), poor conductors of electricity.

4. Coordinate Bond

Coordinate (Dative) Bond: Covalent bond where both shared electrons come from a single atom. Example: NH₄⁺, H₃O⁺.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Octet Rule

Outer shell = 8 electrons

Atoms gain, lose, or share electrons to attain noble gas configuration.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Showing electron transfer for covalent bonds.

✓ Ionic bonds involve complete transfer of electrons from metal to non-metal. Covalent bonds involve sharing of electron pairs between non-metals.

WATCH OUT

✗ Assuming covalent compounds conduct electricity.

✓ Covalent compounds do not have free ions or mobile electrons, so they are poor conductors of electricity.

NCERT exercises (with solutions)

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Multiple Choice Questions

Questions on bond types, octet rule, and compound properties.

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Short Answer Questions

Lewis dot structures, ionic vs covalent properties, and coordinate bonds.

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Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· Concept

State the octet rule.

▶ Show solution

The octet rule states that atoms of elements tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons in their outermost valence shell.

Q2MEDIUM· Structure

Explain the formation of sodium chloride (NaCl) using Lewis notation.

▶ Show solution

1. Sodium (2,8,1) has 1 valence electron and loses it to form Na⁺. 2. Chlorine (2,8,7) has 7 valence electrons and gains 1 electron to form Cl⁻. 3. The electrostatic attraction between Na⁺ and Cl⁻ forms the ionic NaCl bond.

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•Atoms bond to achieve stable octet configuration.
•Ionic bond: transfer of electrons (metal + non-metal).
•Covalent bond: sharing of electrons (non-metal + non-metal).
•Coordinate bond: sharing of electron pair from one atom.
•Ionic compounds: high melting points, soluble in water, conduct in solution/molten state.

Tamil Nadu (TNBSE) marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 4-5 marks in assessments

Question type	Marks each	Typical count	What it tests
MCQ	1	1-2	Base concepts and definitions
Short Answer	2-3	1-2	Descriptive and application points

Prep strategy

Understand core definitions and solve standard textbook problems.
Review common mistakes to avoid losing easy marks.

Where this shows up in the real world

This chapter isn't just an exam topic — it lives in the world around you.

Salt Industries

Ionic compound properties like water solubility are used in table salt production and preservation.

Plastic Manufacturing

Covalent polymers are designed with low melting points and insulation properties for electrical wires.

Exam strategy

Battle-tested tips from teachers and toppers for this chapter.

Write definitions precisely as defined in the textbook.
Draw neat, labeled diagrams for biology and physics chapters.

Going beyond the textbook

For olympiad aspirants and curious learners — topics that build on this chapter.

Read advanced reference materials to explore concepts beyond the school syllabus.

Where else this chapter is tested

CBSE board isn't the only one — other exams test this chapter too.

Class 9 Annual ExamsHigh

NTSE Stage 1Medium

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Questions students ask

The real ones — pulled from the Q&A community and tutor sessions.

They consist of strong electrostatic forces of attraction between oppositely charged ions, which require a large amount of thermal energy to break.

A bond where the shared electron pair is contributed by only one of the bonding atoms (e.g. Formation of ammonium ion, NH₄⁺).

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