Chemical formulae
Chemical formulae
A chemical formula shows which elements are present and the ratio of their atoms. A symbol with no subscript represents one atom, while a subscript shows the number of atoms of the element before it.
Step-by-step lessons on Edexcel GCSE Chemistry 1.1 Formulae, equations and hazards, covering 1.1.1 Formulae, word and balanced equations, 1.1.2 Balanced ionic equations, and 1.1.3 Hazard symbols and risk in practical work. Each one builds up to exam-style questions. Nail the core quantitative topics — moles, balancing equations and calculations — early on, since they underpin higher-tier questions across every paper and topic.