1gCovalent bonding

Syllabus objectives

• 1.44know that a covalent bond is formed between atoms by the sharing of a pair of electrons
• 1.45understand covalent bonds in terms of electrostatic attractions
• 1.46understand how to use dot-and-cross diagrams to represent covalent bonds in: • diatomic molecules, including hydrogen, oxygen, nitrogen, halogens and hydrogen halides • inorganic molecules including water, ammonia and carbon dioxide • organic molecules containing up to two carbon atoms, including methane, ethane, ethene and those containing halogen atoms.
• 1.47explain why substances with a simple molecular structures are gases or liquids, or solids with low melting and boiling points the term intermolecular forces of attraction can be used to represent all forces between molecules
• 1.48explain why the melting and boiling points of substances with simple molecular structures increase, in general, with increasing relative molecular mass
• 1.49explain why substances with giant covalent structures are solids with high melting and boiling points
• 1.50explain how the structures of diamond, graphite and C60 fullerene influence their physical properties, including electrical conductivity and hardness
• 1.51know that covalent compounds do not usually conduct electricity