IGCSE Chemistry Bonding Explained: Ionic, Covalent, Metallic

Understanding chemical bonding is fundamental to IGCSE Chemistry. This complete guide explains ionic, covalent, and metallic bonding, how they form, their properties, and how to identify them, with clear explanations and examples.

What is Chemical Bonding?

Chemical Bonding is the force that holds atoms together to form compounds. Understanding bonding helps explain:

• Why substances have different properties
• How compounds form
• Structure of materials
• Behavior of substances

Key Concept: Atoms bond to achieve stable electron arrangements (full outer shells).

Ionic Bonding

What is Ionic Bonding?

• Transfer of electrons from metal to non-metal
• Forms positive and negative ions
• Ions held together by electrostatic attraction
• Strong attraction = high melting/boiling points

How it Forms:

• Metal atom loses electrons (forms positive ion)
• Non-metal atom gains electrons (forms negative ion)
• Oppositely charged ions attract
• Forms ionic lattice structure

Examples:

• Sodium chloride (NaCl): Na loses electron to Cl
• Magnesium oxide (MgO): Mg loses 2 electrons to O
• Calcium chloride (CaCl₂): Ca loses 2 electrons, 2 Cl atoms each gain 1

Properties:

• High melting and boiling points (strong bonds)
• Conduct electricity when molten or dissolved (ions free to move)
• Soluble in water (polar water molecules break lattice)
• Brittle (layers slide, like charges repel)

Structure:

• Regular lattice structure
• Alternating positive and negative ions
• Strong electrostatic forces
• High density

Covalent Bonding

What is Covalent Bonding?

• Sharing of electrons between non-metal atoms
• Both atoms achieve full outer shells
• Forms molecules
• Can be single, double, or triple bonds

How it Forms:

• Two non-metal atoms share electrons
• Shared pair of electrons
• Both atoms count shared electrons
• Achieve stable electron arrangement

Examples:

• Water (H₂O): H and O share electrons
• Methane (CH₄): C and H share electrons
• Carbon dioxide (CO₂): C and O share electrons (double bonds)
• Oxygen (O₂): Two O atoms share electrons (double bond)

Types of Covalent Bonds:

• Single bond: One shared pair (H-H, H-Cl)
• Double bond: Two shared pairs (O=O, C=O)
• Triple bond: Three shared pairs (N≡N)

Properties:

• Low melting and boiling points (weak intermolecular forces)
• Don’t conduct electricity (no ions, no free electrons)
• Often insoluble in water (non-polar)
• Can be gases, liquids, or solids

Simple vs Giant Covalent:

• Simple molecules: Small molecules (H₂O, CO₂, CH₄)
• Giant covalent: Many atoms bonded (diamond, graphite, silicon dioxide)
• Giant covalent: very high melting points

Metallic Bonding

What is Metallic Bonding?

• Found in metals
• Positive metal ions in sea of delocalized electrons
• Strong attraction between ions and electrons
• Explains metal properties

How it Forms:

• Metal atoms lose outer electrons
• Positive ions form
• Electrons become delocalized (free to move)
• Strong attraction holds structure together

Examples:

• All metals: iron, copper, aluminum, gold
• Metal alloys: steel, brass, bronze
• Metallic structure in all

Properties:

• High melting and boiling points (strong bonds)
• Good conductors of electricity (delocalized electrons)
• Good conductors of heat (electrons transfer energy)
• Malleable and ductile (layers slide, bonds reform)
• Shiny (electrons reflect light)

Structure:

• Regular arrangement of positive ions
• Sea of delocalized electrons
• Strong metallic bonds
• Layers can slide

Comparing Bond Types

Ionic vs Covalent:

• Ionic: metal + non-metal, transfer electrons
• Covalent: non-metal + non-metal, share electrons
• Ionic: high mp/bp, conduct when molten/dissolved
• Covalent: low mp/bp, don’t conduct

Covalent vs Metallic:

• Covalent: non-metals, sharing electrons
• Metallic: metals, delocalized electrons
• Covalent: often gases/liquids
• Metallic: always solids (except mercury)

Ionic vs Metallic:

• Ionic: brittle, conduct when molten/dissolved
• Metallic: malleable, always conduct
• Ionic: soluble in water
• Metallic: insoluble

Identifying Bond Types

From Formula:

• Metal + non-metal = likely ionic
• Non-metal + non-metal = likely covalent
• Metal only = metallic

From Properties:

• High mp/bp + conducts when molten = ionic
• Low mp/bp + doesn’t conduct = covalent (simple)
• High mp/bp + always conducts = metallic
• Very high mp/bp + doesn’t conduct = covalent (giant)

From Structure:

• Lattice of ions = ionic
• Molecules = covalent (simple)
• Giant structure = covalent (giant) or metallic
• Sea of electrons = metallic

Common Mistakes to Avoid

1. Confusing Bond Types

• Ionic: transfer of electrons
• Covalent: sharing of electrons
• Metallic: delocalized electrons
• Know the differences clearly

2. Properties Confusion

• Don’t confuse structure with properties
• Understand why properties occur
• Link structure to properties

3. Drawing Structures

• Ionic: show ions clearly
• Covalent: show shared pairs
• Metallic: show ions and electrons
• Use correct symbols

Related Resources

• IGCSE Chemistry Revision Notes
• IGCSE Chemistry Past Papers
• IGCSE Chemistry Tutor

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Understanding bonding is essential for IGCSE Chemistry. Practice regularly and seek help when needed to master this fundamental concept.