Classroom revision quiz (16.10.2014)
The physical and chemical properties of compounds depend on the ways in which the compounds are held together by chemical bonds and by intermolecular forces.
Theories of bonding explain how atoms or ions are held together in these structures.
Materials scientists use knowledge of structure and bonding to engineer new materials with desirable properties.
These new materials may offer new applications in a range of different modern technologies.
- 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: • predict the charge on a simple ion using the position of the element in the Periodic Table • construct formulas for ionic compounds
- 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. How do co-ordinate bonds form, simulation by boardworks (click here) Dative covalent bond, simulation by boardworks (click here) Students should be able to represent: • a covalent
- Metallic bonding - Metallic bonding involves attraction between delocalised electrons and positive ions arranged in a lattice.
- Bonding and physical properties - The four types of crystal structure: • ionic • metallic • macromolecular (giant covalent) • molecular. The structures of the following crystals as examples of these four types of crystal structure: • diamond • graphite • ice • iodine • magnesium • sodium chloride. Assessment and practical opportunities Students should be able to: • relate the melting point and conductivity of
- Shapes of simple molecule 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: VSEPR (valence shell electron pair repulsion) The effect of electron pair repulsion influences bond angles Students should be able to: • explain the shapes of, and bond angles
- Bond polarity - Electronegativity is the tendency of an atom to attract electron density from a shared pair of electrons contained in a covalent bond. The electron distribution in a covalent bond between elements with different electronegativities will be asymmetrical. This produces a polar covalent bond, and may cause a molecule to have a permanent dipole. In general, Electronegativity increases across the periodic table– due to successive
- Forces between molecules - Forces between molecules: • permanent dipole–dipole forces • induced dipole–dipole (van der Waals, dispersion, London) forces • 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. Assessment and practical opportunities Students should be
- Revision notes for Bonding AS - These student notes have been produced by Pearson Schools aimed at the Edexcel syllabus and are available directly from Perason Schools for free (click here)
- AS Bonding worksheet from RSC -