Formula types and bond counting
Formula types and bond counting

Organic chemistry at IGCSE is mainly about carbon compounds. Carbon usually forms 4 covalent bonds, hydrogen forms 1, and oxygen forms 2, so bond-counting helps you spot impossible displayed formulae.
Step-by-step lessons on CIE IGCSE Chemistry Formulae, functional groups and terminology. Each one builds up to exam-style questions. Build a solid grasp of atomic structure, bonding and the mole concept early, since these underpin almost every other topic, then move on to the more calculation-heavy quantitative and organic chemistry content.