ChemistryCode 9701
Covalent bonding and coordinate (dative covalent) bonding
What this topic asks you to be able to do
- define covalent bonding as the electrostatic attraction between a pair of electrons shared by two atoms and the nuclei of those atoms (a) describe the covalent bonding in molecules including: • hydrogen, H2 • oxygen, O2 • nitrogen, N2 • chlorine, Cl2 • hydrogen chloride, HCl • carbon dioxide, CO2 • ammonia, NH3 • methane, CH4 • ethane, C2H6 • ethene, C2H4 (b) understand that an element of period 3 can expand its octet, as happens in compounds including sulfur dioxide, SO2, phosphorus pentachloride, PCl5, and sulfur hexafluoride, SF6 (c) describe coordinate (dative covalent) bonding, including when gaseous ammonia and hydrogen chloride combine to give the ammonium ion, NH4+, and within the Al2Cl6 molecule
- describe how covalent bonds arise from orbital overlap, yielding σ and π bonds: • σ bonds result from orbitals overlapping directly between the bonding atoms • π bonds result from adjacent p orbitals overlapping sideways, above and below the σ bond (b) describe the way σ and π bonds are created in molecules including H₂, C₂H₆, C₂H₄, HCN and N₂ (c) apply the idea of hybridisation when describing sp, sp² and sp³ orbitals
- define these terms: • bond energy, the energy taken in when one mole of a specific covalent bond is broken in the gaseous state • bond length, the internuclear distance between two atoms joined by a covalent bond (b) use bond energy values, together with the idea of bond length, to compare how reactive covalent molecules are