1.3Physical Chemistry

Bonding — Oxford AQA International A Level Chemistry Revision Notes & Topical Questions

10 min read 26 parts Lesson 3 of 13

📚 Oxford AQA International A Level Chemistry Hub / Topical Revision

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Lesson summary

Complete PDF with figures and original page layoutPage 1 Oxford AQA International Your notes A Level (IAL) Chemistry Bonding Contents Ionic Bonding Nature of Covalent & Dative Covalent Bonds Metallic Bonding Bonding & Physical Properties Shapes of …

Part 1 of 9Ionic bonding

Ionic bonding = the electrostatic attraction between oppositely charged ions in a lattice

2Process

Process electrons transfer from a metal to a non-metal, usually giving both a full outer shell

3Cations

Cations metals lose valence electrons to form positive ions such as Na⁺, K⁺, Mg²⁺ and Ca²⁺

4Anions

Anions non-metals gain electrons to form negative ions such as F^-, Cl^-, O^2- and N^3-

5Charge

Charge it equals the number of electrons lost or gained

6Noble gas configuration

Noble gas configuration sodium ion 1s²2s²2p⁶ and chloride ion 1s²2s²2p⁶3s²3p⁶, like argon

Part 2 of 9Ionic lattices

Formation

Formation an electron transfers from Na to Cl, and the two oppositely charged ions bond together

Lattice

Lattice a regular repeating crystalline arrangement in which ions are attracted in all directions

Neutrality

Neutrality positive charges cancel negative charges, so the lattice is electrically neutral

Part 3 of 9Ion charges and compound ions

Group	Ion charge	Example
1	1+	K⁺
2	2+	Sr²⁺
3	3+	Al³⁺
5	3-	N^3-
6	2-	S^2-
7	1-	I^-

Ion	Charge	Formula
Sulfate	2-	SO₄^2-
Hydroxide	1-	OH^-
Nitrate	1-	NO₃^-
Carbonate	2-	CO₃^2-
Ammonium	1+	NH₄⁺

Formula
- balance charges to a neutral compound,
- so sodium carbonate is Na₂CO₃, copper(II) nitrate is Cu(NO₃)₂, ammonium sulfate is (NH₄)₂SO₄ and magnesium hydroxide is Mg(OH)₂

Part 4 of 9Covalent bonding

Covalent bond

Covalent bond the electrostatic attraction between the nuclei of two atoms and the shared bonding electrons, occurring between non-metals

No transfer

No transfer electrons are shared, giving each atom a noble gas configuration and greater stability

Bond	Example	Electrons shared
Single	C–C	2
Double	C=C	4
Triple	C≡C	6

Examples
- Cl₂, HCl, NH₃, CH₄, CO₂, C₂H₄ and N₂

Part 5 of 9Dative covalent bonding

Dative covalent (coordinate) bond = a covalent bond in which both shared electrons come from the same atom

Requirement

Requirement one atom has a lone pair and the other is electron-deficient with an unfilled outer orbital

Ammonium ion

Ammonium ion the nitrogen lone pair in ammonia is donated to the electron-deficient H⁺, forming NH₄⁺

Drawing

Drawing an arrow shows the pair coming from the same atom

Part 6 of 9Metallic bonding

Metallic bonding

Structure

Structure metal atoms are tightly packed in a regular lattice

Delocalised electrons

Delocalised electrons outer electrons are free to move through the structure and are not bound to their atom

Positive ions

Positive ions the atoms become positive ions that repel each other and keep the lattice in place

Metallic bond

Metallic bond very strong electrostatic attraction between the positive metal ions and the sea of delocalised electrons

Part 7 of 9States of matter and crystals

State	Density	Arrangement	Movement	Energy
Solid	High	Regular pattern	Vibrate about fixed positions	Low
Liquid	Medium	Random	Move around each other	Greater
Gas	Low	Random	Move quickly in all directions	Highest

Changes of state

Changes of state melting (fusion) is solid to liquid, and boiling (vaporisation) is liquid to gas

Crystals

Crystals solids held by ionic, metallic or covalent bonds or intermolecular forces, and the stronger the forces, the higher the enthalpy of fusion

Part 8 of 9Properties of ionic compounds

1Brittle

Brittle layers shift and like charges align, so the crystal splits

2High melting and boiling points

High melting and boiling points strong electrostatic forces act in all directions

3Charge density

Charge density melting point rises with ion charge, so MgO melts higher than NaCl

4Not volatile

Not volatile a large amount of energy is needed to overcome the forces

5Solubility

Solubility they are generally soluble in water because they form ion-dipole interactions

6Conductivity

Conductivity they conduct only when molten or in solution, since the ions are fixed in position in the solid

Part 9 of 9Properties of metals

Malleability

Malleability layers of ions slide over each other
Attraction acts in all directions, so metallic bonds re-form as layers move.
The lattice is not broken, only reshaped.

Strength and hardness

Strength and hardness strong attraction between the metal ions and delocalised electrons

Conductivity

Conductivity metals conduct as solids and liquids because the electrons are mobile
Under a potential difference, electrons move towards the positive terminal.
Conductivity increases across a period as outer electrons increase, from Na (1) to Mg (2) to Al (3).

Key terms

Term	Meaning
Ionic bonding	The electrostatic attraction between oppositely charged ions in a lattice.
Covalent bond	The attraction between nuclei and a shared pair of electrons.
Dative covalent bond	A covalent bond in which both electrons come from one atom.
Delocalised electrons	Outer electrons free to move through a metal lattice.
Lattice	A regular repeating arrangement of particles.
Volatility	How easily a substance vaporises.

Avoid these mistakes

Saying ionic compounds conduct as solids — the ions cannot move in the solid.

Saying a dative bond differs in strength — it is identical once formed, but both electrons come from one atom.

Saying metals are held together by shared electrons — they are held by attraction between ions and delocalised electrons.

Saying ionic compounds are malleable — they are brittle.

Last updated: 18 October 2026