12.13: Factors affecting basicity (proton binding) 13.10: Proton Donation and Structure 13.11: Factors affecting Bronsted-Lowry Acidity: Local Factors 13.12: Factors affecting Bronsted-Lowry Acidity: Distal Factors 13.14: Direction of Proton Transfer 13.15: pKa and Amino Acids 13.16: Solvent Effects-Relative Conditions and pKa 13.17: The Meaning of pKa: Product-to-Reactant Ratio and Equilibrium Constant 13.18: pH and Buffers 13.19: Application Problems 13.1: General Acidity and Basicity 13.20: Solutions to Selected Problems 13.2: Lewis Bases 13.3: Lewis Acids 13.4a: Lewis Acid-Base Complexes 13.4b: Molecular Orbital Interactions in Lewis Acid-Base Reactions 13.5: Reversibility of the Coordinate Bond 13.6: Coordination Complexes The bond that forms between a Lewis base and a Lewis acid is sometimes called a dative bond or a coordinate bond. The term used for the donation of a Lewis base to a Lewis acid, without any other bonding changes, is coordination. Another term for Lewis acid-base complexes, especially used in the context of transition metal chemistry, is coordination complexes. Sometimes the Lewis base is referred to as a ligand; more generally, a ligand is just one molecule that binds to another. 13.7: Proton as a Common Lewis Acid Perhaps the most common example of a Lewis acid or electrophile is also the simplest. It is the hydrogen cation or proton. It is called a proton because, in most hydrogen atoms, the only particle in the nucleus is a proton. If an electron is removed to make a cation, a proton is all that is left. 13.8a: Proton Transfer from One Basic Site to Another 13.8b: Molecular Orbital Interactions in Proton Transfers 13.9: Proton Donor Strength: pKa