Chemical bonding

Learning objectives

Explain what determines electronegativity and its trends across a period and down a group, and use Pauling electronegativity differences to predict whether a bond is ionic, polar covalent or non-polar

Describe ionic, metallic, covalent and coordinate (dative) bonding with dot-and-cross diagrams, including NaCl, MgO, CaF₂, NH₄⁺, Al₂Cl₆ and the expanded octets in SO₂, PCl₅ and SF₆

Describe σ and π bonds as end-on and sideways orbital overlap, and use sp, sp² and sp³ hybridisation to explain the bonding in molecules such as C₂H₆, C₂H₄, HCN and N₂

Use VSEPR theory to predict and explain the shapes and bond angles of molecules and ions such as BF₃, CO₂, CH₄, NH₃, H₂O, PF₅ and SF₆

Use bond energy and bond length to compare the reactivity of covalent molecules, and explain the polarity of a molecule from its bond dipoles and its shape

Describe instantaneous dipole–induced dipole forces, permanent dipole–permanent dipole forces and hydrogen bonding, and use them to explain boiling points and the unusual properties of water and ice