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*Revision Materials and Past Papers* 2.1.1 Atomic structure and isotopes 2.1.2 Compounds, formulae and equations 2.1.3 Amount of substance 2.1.4 Acids 2.1.5 Redox 2.2.1 Electron structure 2.2.2 Bonding and structure 3.1.1 Periodicity 3.1.2 Group 2 3.1.3 The halogens 3.1.4 Qualitative analysis 3.2.1 Enthalpy 3.2.2 Reaction Rates 3.2.3 Chemical equilibrium 4.1 Basic concepts and hydrocarbons 4.1.2 Alkanes 4.1.3 Alkenes 4.2.1 Alcohols 4.2.2 Haloalkanes 4.2.3 Organic synthesis 4.2.4 Analytical techniques 5.1.1 How fast? 5.1.2 How far? 5.1.3 Acids, bases and buffers 5.2.1 Lattice enthalpy 5.2.2 Enthalpy and entropy 5.2.3 Redox and electrode potentials 5.3.1 Transition elements 5.3.2 Qualitative analysis 6.1.1 Aromatic compounds 6.1.2 Carbonyl compounds 6.1.3 Carboxylic acids and esters 6.2.1 Amines 6.2.2 Amino acids, amides and chirality 6.2.3 Polyesters and polyamides 6.2.4 Carbon–carbon bond formation 6.2.5 Organic synthesis 6.3.1 Chromatography and qualitative analysis 6.3.2 Spectroscopy Required Practicals

2.2.2 Bonding and structure

Covalent bondingElectronegativity and bond polarityIntermolecular forcesIonic bondingThe shapes of simple molecules and ions

Ionic Bonding

Specification Reference 2.2.2 (a)–(o)

Quick Notes

  • Ionic bonding: strong electrostatic attraction between oppositely charged ions
  • Electron transfer between atoms can be represented using dot-and-cross diagrams
  • Ionic compounds have:
    • High melting and boiling points due to strong forces of attraction between ions
    • High electrical conductivity when molten or in solution, as charged ions are free to move (unable to conduct electricity when solid)

Full Notes

Ionic Bonding

Ionic bonding is the strong electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions) in an ionic compound.

Ions are formed when atoms lose or gain electrons (forming cations and anions). The resulting electrostatic attraction between the oppositely charged ions forms a strong ionic bond.

Dot-and-cross diagrams can be used show the transfer of electrons clearly.

Example Sodium chloride (NaCl)

OCR (A) A-Level Chemistry dot-and-cross diagram showing ionic bonding in sodium chloride NaCl.

Sodium atom (Na) loses one electron → Na+
Chlorine atom (Cl) gains one electron → Cl−
Ions combine to form NaCl, held in a lattice.

Giant Ionic Lattices

Ionic compounds exist as a regular, 3D lattice of positive and negative ions (e.g. Na+ and Cl− in NaCl).

Each ion is surrounded by oppositely charged ions, giving the structure strength and stability.

OCR (A) A-Level Chemistry diagram showing the 3D giant ionic lattice of sodium chloride NaCl.

Properties of Ionic Compounds

Summary