2.2.2
Bonding and Structure
OCR 2.2.2 covers the covalent bond and dot-and-cross diagrams, dative bonding, average bond enthalpy, the shapes and bond angles of molecules and ions predicted by electron pair repulsion, electronegativity and the polarity of bonds and molecules. The section also covers ionic and metallic bonding, simple molecular and giant lattices, and intermolecular forces with hydrogen bonding and the anomalous properties of water.
Revision Notes
Work through each part of OCR 2.2.2 in a structured sequence.
Bonding
Covalent Bonding
The covalent bond, sigma and pi bonds, dative bonds, giant covalent structures and electronegativity (2.2.2(d)-(f), (i)).
Start revisingMolecules
Shapes of Molecules
Electron pair repulsion, the shapes and bond angles of molecules and ions with up to six electron pairs (2.2.2(g)-(h)).
Start revisingMolecules
Non-Polar and Polar Molecules
Polar bonds, permanent dipoles and whether a molecule is polar overall (2.2.2(j)).
Start revisingBonding
Ionic Bonding
Ionic bonding and dot-and-cross diagrams, giant ionic lattices, polarisation and the properties of ionic compounds (2.2.2(a)-(c)).
Start revisingMetallic Bonding
Metal ions in a sea of delocalised electrons, and how the model explains conductivity, malleability and melting points.
Start revisingMolecular
Simple Molecular Structures
Iodine and ice as simple molecular lattices: covalent bonds inside the molecules, weak forces between them (2.2.2(n)-(o)).
Start revisingTypes
Structure Types
Giant ionic, giant metallic, giant covalent and simple molecular lattices compared, and deducing structure and bonding from properties.
Start revisingEnthalpy
Bond Enthalpy and Pauling Values
Average bond enthalpy as a measure of bond strength, and reading the Pauling electronegativity scale (2.2.2(f), (i)).
Start revisingForces
Intermolecular Forces
Induced and permanent dipole-dipole interactions, hydrogen bonding, the anomalous properties of water, boiling point trends and solubility (2.2.2(k) to (o)).
Start revising2.2.2 Bonding and Structure – OCR A Level Chemistry A
The following OCR learning outcomes for covalent bonding, shapes and polarity are covered by these pages. The ionic bonding, metallic bonding and lattice pages are now included; the intermolecular forces outcomes (k) to (m) follow with a later topic.
2.2.2 Bonding and structure (covalent bonding, shapes and polarity)
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:
Use of the term average bond enthalpy as a measurement of covalent bond strength.
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.
Electron pair repulsion to explain the following shapes of molecules and ions:
Electronegativity as the ability of an atom to attract the bonding electrons in a covalent bond; interpretation of Pauling electronegativity values.
Explanation of: