ionic bonding as electrostatic attraction between positive and negative ions, and the construction of 'dot-and-cross' diagrams

explanation of the solid structures of giant ionic lattices, resulting from oppositely charged ions strongly attracted in all directions e.g. NaCl

explanation of the effect of structure and bonding on the physical properties of ionic compounds, including melting and boiling points, solubility and electrical conductivity in solid, liquid and aqueous states

covalent bond as the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

construction of ‘dot-and-cross’ diagrams of molecules and ions to describe:

(i) single covalent bonding
(ii) multiple covalent bonding
(iii) dative covalent (coordinate) bonding

‘Dot-and-cross’ diagrams of up to six electron pairs (including lone pairs) surrounding a central atom.

use of the term average bond enthalpy as a measurement of covalent bond strength

Learners should appreciate that the larger the value of the average bond enthalpy, the stronger the covalent bond.
Definition and calculations not required.
Average bond enthalpies and related calculations are covered in detail in 3.2.1f.

the shapes of, and bond angles in, molecules and ions with up to six electron pairs (including lone pairs) surrounding the central atom as predicted by electron pair repulsion, including the relative repulsive strengths of bonded pairs and lone pairs of electrons

Learners should be able to draw 3-D diagrams to illustrate shapes of molecules and ions.

electron pair repulsion to explain the following shapes of molecules and ions: linear, non-linear, trigonal planar, pyramidal, tetrahedral and octahedral

Learners are expected to know that lone pairs repel more than bonded pairs and the bond angles for common examples of each shape including CH₄ (109.5°), NH₃ (107°) and H₂O (104.5°).

electronegativity as the ability of an atom to attract the bonding electrons in a covalent bond; interpretation of Pauling electronegativity values

Learners should be aware that electronegativity increases towards F in the periodic table.

explanation of:

(i) a polar bond and permanent dipole within molecules containing covalently-bonded atoms with different electronegativities
(ii) a polar molecule and overall dipole in terms of permanent dipole(s) and molecular shape

A polar molecule requires polar bonds with dipoles that do not cancel due to their direction. E.g. H₂O and CO₂ both have polar bonds but only H₂O has an overall dipole.

intermolecular forces based on permanent dipole–dipole interactions and induced dipole–dipole interactions

Permanent dipole–dipole and induced dipole–dipole interactions can both be referred to as van der Waals’ forces.
Induced dipole–dipole interactions can also be referred to as London (dispersion) forces.

hydrogen bonding as intermolecular bonding between molecules containing N, O or F and the H atom of –NH, –OH or HF

Including the role of lone pairs.

explanation of anomalous properties of H₂O resulting from hydrogen bonding, e.g.:

(i) the density of ice compared with water
(ii) its relatively high melting and boiling points

explanation of the solid structures of simple molecular lattices, as covalently bonded molecules attracted by intermolecular forces, e.g. I₂, ice

explanation of the effect of structure and bonding on the physical properties of covalent compounds with simple molecular lattice structures including melting and boiling points, solubility and electrical conductivity.