IGCSE Ions and Ionic Bonds: Complete Guide for Cambridge IGCSE Chemistry

IGCSE ions and ionic bonds are fundamental topics in Cambridge IGCSE Chemistry that explain how atoms gain or lose electrons to form charged particles and how these particles bond together. Mastering ion formation, ionic bonding, and properties of ionic compounds is essential for achieving top grades in IGCSE Chemistry exams.

This comprehensive IGCSE ions and ionic bonds guide covers everything you need to know, including what ions are, how they form, ionic bonding processes, dot-and-cross diagrams, properties of ionic compounds, step-by-step worked examples, common exam questions, and expert tips from Tutopiya’s IGCSE chemistry tutors. We’ll also show you how to avoid the most common mistakes that cost students valuable marks.

🎯 What you’ll learn: By the end of this guide, you’ll know how ions form, draw dot-and-cross diagrams for ionic compounds, explain ionic bonding, understand properties of ionic compounds, and apply these concepts to solve problems in IGCSE Chemistry exams.

Already studying with Tutopiya? Practice these skills with our dedicated IGCSE Chemistry practice deck featuring exam-style questions and instant feedback.

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Why IGCSE Ions and Ionic Bonds Matter

IGCSE ions and ionic bonds are essential topics that appear throughout the IGCSE Chemistry curriculum. Here’s why they’re so important:

• Foundation topic: Required for understanding all bonding and compound formation
• High frequency: Questions about ionic bonding appear in almost every IGCSE chemistry paper
• Exam weight: Typically worth 8-12 marks per paper
• Real-world applications: Essential for understanding salts, electrolytes, and many compounds
• Link to other topics: Connects to atomic structure, the periodic table, and chemical reactions

Key insight from examiners: Students often struggle with drawing dot-and-cross diagrams or explaining why ionic compounds have certain properties. This guide will help you master these concepts systematically.

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Understanding Ions

An ion is an atom or group of atoms that has gained or lost electrons, resulting in a positive or negative charge.

Types of Ions

Cations (Positive Ions):

• Formed when: Atoms lose electrons
• Charge: Positive (+)
• Examples: Na⁺, Mg²⁺, Al³⁺
• Formed from: Metals (usually)

Anions (Negative Ions):

• Formed when: Atoms gain electrons
• Charge: Negative (-)
• Examples: Cl⁻, O²⁻, F⁻
• Formed from: Non-metals (usually)

Formation of Ions

Cations: Metal atoms lose electrons to achieve stable electron configuration (usually full outer shell like noble gases)

Example: Sodium (Na) → Sodium ion (Na⁺)

• Sodium atom: 2,8,1 (11 electrons, 11 protons)
• Loses 1 electron
• Sodium ion: 2,8 (10 electrons, 11 protons)
• Charge: +1

Anions: Non-metal atoms gain electrons to achieve stable electron configuration

Example: Chlorine (Cl) → Chloride ion (Cl⁻)

• Chlorine atom: 2,8,7 (17 electrons, 17 protons)
• Gains 1 electron
• Chloride ion: 2,8,8 (18 electrons, 17 protons)
• Charge: -1

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Ionic Bonding

Ionic bonding occurs when metal atoms transfer electrons to non-metal atoms, forming oppositely charged ions that attract each other.

Process of Ionic Bonding

1. Metal atom loses electron(s) → forms cation
2. Non-metal atom gains electron(s) → forms anion
3. Opposite charges attract → ionic bond forms
4. Ionic compound results (electrically neutral overall)

Example: Sodium Chloride (NaCl)

Formation:

• Sodium (Na) loses 1 electron → Na⁺
• Chlorine (Cl) gains 1 electron → Cl⁻
• Na⁺ and Cl⁻ attract → ionic bond
• Formula: NaCl

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Dot-and-Cross Diagrams

Dot-and-cross diagrams show how electrons are transferred in ionic bonding.

Rules for Drawing

• Dots (•): Represent electrons from one atom
• Crosses (×): Represent electrons from the other atom
• Square brackets: Show ions with their charges
• Only show outer shell electrons

Example: Sodium Chloride (NaCl)

Na atom          Cl atom
[Na]•            ×××[Cl]××××
               
After transfer:
[Na]⁺            [××××Cl××××]⁻

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Properties of Ionic Compounds

High Melting and Boiling Points

• Why: Strong electrostatic forces between oppositely charged ions
• Requires: Lots of energy to break the ionic lattice
• Example: Sodium chloride melts at 801°C

Soluble in Water

• Why: Water molecules can surround and separate ions
• Process: Hydration (water molecules attract ions)
• Result: Ions separate and dissolve

Conduct Electricity When Molten or Dissolved

• Why: Ions are free to move and carry charge
• Solid: Ions fixed in position, cannot conduct
• Molten/Dissolved: Ions free to move, can conduct

Brittle

• Why: Ions are arranged in a rigid lattice
• When struck: Ions of same charge come together, repel
• Result: Lattice shatters

Crystal Structure

• Why: Ions pack in a regular, repeating pattern
• Forms: Ionic lattice (giant structure)
• Shape: Regular crystals

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Common Ionic Compounds

Group 1 + Group 7:

• NaCl (sodium chloride)
• KCl (potassium chloride)
• LiF (lithium fluoride)

Group 2 + Group 7:

• MgCl₂ (magnesium chloride)
• CaCl₂ (calcium chloride)

Group 1 + Group 6:

• Na₂O (sodium oxide)
• K₂O (potassium oxide)

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Worked Examples

Example 1: Ion Formation

Explain how a magnesium ion (Mg²⁺) is formed.

Solution:

1. Magnesium atom has electron configuration 2,8,2 (12 electrons)
2. To achieve stable configuration (like neon: 2,8), it needs to lose 2 electrons
3. Magnesium loses 2 electrons → Mg²⁺
4. New configuration: 2,8 (10 electrons, 12 protons)
5. Charge: +2 (2 more protons than electrons)

Example 2: Ionic Bonding

Explain how magnesium chloride (MgCl₂) is formed.

Solution:

1. Magnesium (Mg) loses 2 electrons → Mg²⁺
2. Two chlorine atoms (Cl) each gain 1 electron → 2Cl⁻
3. Mg²⁺ attracts two Cl⁻ ions → ionic bonds form
4. Formula: MgCl₂ (1 Mg²⁺ and 2 Cl⁻)

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Common Examiner Traps

• Wrong ion charges - Remember Group 1 → +1, Group 2 → +2, Group 7 → -1, Group 6 → -2
• Incorrect formulas - Charges must balance (overall neutral)
• Dot-and-cross mistakes - Use different symbols for different atoms’ electrons
• Properties explanations - Always link to ionic lattice structure

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Practice Questions

Question 1

Explain how calcium oxide (CaO) is formed by ionic bonding.

Solution:

• Calcium (Ca) loses 2 electrons → Ca²⁺ (to achieve stable configuration)
• Oxygen (O) gains 2 electrons → O²⁻ (to achieve stable configuration)
• Ca²⁺ and O²⁻ attract → ionic bond forms
• Formula: CaO

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• Live whiteboard walkthroughs of ionic bonding and dot-and-cross diagrams
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Frequently Asked Questions

What is an ion?

An ion is an atom or group of atoms that has gained or lost electrons, giving it a positive or negative charge.

How do cations form?

Cations (positive ions) form when atoms lose electrons, usually metals trying to achieve stable electron configuration.

How do anions form?

Anions (negative ions) form when atoms gain electrons, usually non-metals trying to achieve stable electron configuration.

What is ionic bonding?

Ionic bonding is the electrostatic attraction between oppositely charged ions, formed when electrons are transferred from metal to non-metal atoms.

Why do ionic compounds have high melting points?

Strong electrostatic forces between oppositely charged ions in the ionic lattice require lots of energy to overcome.

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Related IGCSE Chemistry Resources

• IGCSE Covalent Bonds Guide - Master covalent bonding
• IGCSE Atomic Structure Guide - Master atomic structure
• IGCSE Chemistry Revision Notes - Complete syllabus overview

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Next Steps: Master IGCSE Ions and Ionic Bonds with Tutopiya

Ready to excel in IGCSE ions and ionic bonds? Our expert IGCSE chemistry tutors provide personalized 1-on-1 tutoring, exam-focused practice, and interactive whiteboard sessions.

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