Edexcel IAL Chemistry Topic 3 Checklist
(2025–2026 Exams)
Topic 3: Bonding and Structure
3A: Ionic Bonding
Know and be able to interpret evidence for the existence of ions
, limited to physical properties of ionic compounds, electron density maps and the migration of ions
Be able to describe the formation of ions
in terms of loss or gain of electrons
Be able to draw dot-and-cross diagrams
to show electrons in cations and anions
Be able to describe ionic crystals
as giant lattices of ions
Know that ionic bonding
is the result of strong net electrostatic attraction between ions
Understand the effects of ionic radius
and ionic charge
on the strength of ionic bonding
Understand reasons for the trends in ionic radii
down a group in the Periodic Table, and for a set of isoelectronic ions, including N 3−
to Al 3+
Understand the meaning of the term ‘ polarisation
’ as applied to ions
Understand that the polarising power
of a cation depends on its radius and charge, and the polarisability
of an anion also depends on its radius and charge
Further suggested practical:
The migration of ions in a U-tube using copper(II) chromate solution or on a microscope slide using potassium manganate(VII) crystals
3B: Covalent Bonding
Understand that covalent bonding
is the strong electrostatic attraction between two nuclei and the shared pair of electrons between them, based on the evidence: the physical properties of giant atomic structures and electron density maps for simple molecules
Be able to draw dot-and-cross diagrams
to show electrons in covalent substances, including:
– Molecules with single, double and triple bonds
– Species with dative covalent (coordinate) bonds, including Al 2 Cl 6 and the ammonium ion
– Molecules with single, double and triple bonds
– Species with dative covalent (coordinate) bonds, including Al 2 Cl 6 and the ammonium ion
Be able to describe the different structures formed by giant lattices of carbon atoms
, including graphite, diamond and graphene, and discuss the applications of each
Understand the meaning of the term ‘ electronegativity
’ as applied to atoms in a covalent bond
Know that ionic
and covalent bonding
are the extremes of a continuum of bonding type and be able to explain this in terms of electronegativity differences, leading to bond polarity in bonds and molecules, and to ionic bonding if the electronegativity is large enough
Be able to distinguish between polar bonds
and polar molecules
and predict whether or not a given molecule is likely to be polar
Further suggested practical:
Determine the effect of an electrostatic force on jets of liquids (water, ethanol and cyclohexane) and use the results to determine whether the molecules are polar or non-polar
3C: Shapes of Molecules
Understand the principles of the electron-pair repulsion theory
, used to interpret and predict the shapes of simple molecules and ions
Understand the terms ‘ bond length
’ and ‘ bond angle
’
Know and be able to explain the shapes of, and bond angles in, BeCl 2
, BCl 3
, CH 4
, NH 3
, NH 4
+
, H 2
O
, CO 2
, gaseous PCl 5
, SF 6
and C 2
H 4
Be able to apply the electron-pair repulsion theory
to predict the shapes of, and bond angles in, molecules and ions analogous to those in 3.18
3D: Metallic Bonding
Understand that metals
consist of giant lattices of metal ions in a sea of delocalised electrons
Know that metallic bonding
is the strong electrostatic attraction between metal ions and the delocalised electrons
Be able to use the models in 3.20 and 3.21 to interpret simple properties of metals, including electrical conductivity
and high melting temperature
