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AQA A Level Chemistry

3.1.3
Bonding

AQA 3.1.3 covers ionic, covalent and metallic bonding, bonding and physical properties, shapes of molecules and ions, bond polarity and intermolecular forces. This topic links structure, bonding and forces to melting point, conductivity, crystal structure and molecular shape.

Exam Paper
Paper 1
7405/1
Specification Points
3.1.3.1 – 3.1.3.7
7 AQA sections
Topic Parts
8 parts
Revision notes available
Exam Board
AQA
AQA 7405

Revision Notes

Work through each part of AQA 3.1.3 in a structured sequence.

Ionic bonding
Ionic
Bonding
1
Available

Ionic Bonding

Electrostatic attraction between oppositely charged ions in a lattice, ionic formulae and properties.

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Shared pairs
Covalent
Bonding
2
Available

Covalent Bonding

Single, multiple and dative covalent bonds, including line and arrow representations.

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Electron pairs
Shapes of
Molecules
3
Available

Shapes of Molecules and Ions

Electron-pair repulsion, lone pairs, bond angles and shapes of simple molecules and ions.

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Partial charges
Bond
Polarity
4
Available

Bond Polarity

Electronegativity, polar covalent bonds and why some molecules have permanent dipoles.

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Delocalised electrons
Metallic
Bonding
5
Available

Metallic Bonding

Attraction between delocalised electrons and positive ions arranged in a lattice.

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Macromolecular
Giant
Covalent
6
Available

Giant Covalent Structures

Macromolecular structures such as diamond and graphite, and their properties.

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Molecular crystals
Simple
Molecular
7
Available

Simple Molecular Structures

Molecular substances such as iodine and ice, including melting point and conductivity.

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Lattices
Structure
Types
8
Available

Structure Types

Giant ionic, giant metallic, giant covalent and simple molecular lattices compared: melting point, conductivity, solubility and energy changes on changes of state (3.1.3.4).

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Forces between molecules
Intermolecular
Forces
9
Available

Intermolecular Forces

London forces, permanent dipole-dipole forces and hydrogen bonding.

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Specification Coverage

3.1.3 Bonding – AQA A Level Chemistry

The following AQA specification points outline the knowledge and skills students are expected to demonstrate for Bonding.

3.1.3 Bonding

3.1.3.1
Ionic bonding
Ionic bonding involves electrostatic attraction between oppositely charged ions in a lattice.
The formulas of compound ions, eg sulfate, hydroxide, nitrate, carbonate and ammonium.
Students should be able to:
1
predict the charge on a simple ion using the position of the element in the Periodic Table
2
construct formulas for ionic compounds.
3.1.3.2
Nature of covalent and dative covalent bonds
A single covalent bond contains a shared pair of electrons.
Multiple bonds contain multiple pairs of electrons.
A co-ordinate (dative covalent) bond contains a shared pair of electrons with both electrons supplied by one atom.
Students should be able to represent:
1
a covalent bond using a line
2
a co-ordinate bond using an arrow.
3.1.3.3
Metallic bonding
Metallic bonding involves attraction between delocalised electrons and positive ions arranged in a lattice.
3.1.3.4
Bonding and physical properties
The four types of crystal structure:
1
ionic
2
metallic
3
macromolecular (giant covalent)
4
molecular.

The structures of the following crystals as examples of these four types of crystal structure:
1
diamond
2
graphite
3
ice
4
iodine
5
magnesium
6
sodium chloride.

Students should be able to:
1
relate the melting point and conductivity of materials to the type of structure and the bonding present
2
explain the energy changes associated with changes of state
3
draw diagrams to represent these structures involving specified numbers of particles.
3.1.3.5
Shapes of simple molecules and ions
Bonding pairs and lone (non-bonding) pairs of electrons as charge clouds that repel each other.
Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repulsion.
Lone pair-lone pair repulsion is greater than lone pair-bond pair repulsion, which is greater than bond pair-bond pair repulsion.
The effect of electron pair repulsion on bond angles.
Students should be able to:
1
explain the shapes of, and bond angles in, simple molecules and ions with up to six electron pairs (including lone pairs of electrons) surrounding the central atom.
3.1.3.6
Bond polarity
Electronegativity as the power of an atom to attract the pair of electrons in a covalent bond.
The electron distribution in a covalent bond between elements with different electronegativities will be unsymmetrical. This produces a polar covalent bond, and may cause a molecule to have a permanent dipole.
Students should be able to:
1
use partial charges to show that a bond is polar
2
explain why some molecules with polar bonds do not have a permanent dipole.
3.1.3.7
Forces between molecules
Forces between molecules:
1
permanent dipole-dipole forces
2
induced dipole-dipole (van der Waals, dispersion, London) forces
3
hydrogen bonding.

The melting and boiling points of molecular substances are influenced by the strength of these intermolecular forces.
The importance of hydrogen bonding in the low density of ice and the anomalous boiling points of compounds.
Students should be able to:
1
explain the existence of these forces between familiar and unfamiliar molecules
2
explain how melting and boiling points are influenced by these intermolecular forces.