Writing formulae correctly underpins almost everything in Chemistry. Get the formula wrong and our equation will not balance, our molar mass calculation will be off, and our ionic equation will fall apart. It is a foundational skill — and one that rewards genuine understanding over memorisation.
EdTechSims offers three free interactive games that build formula writing fluency from the ground up, each targeting a different stage of the skill.
Game 1: Formula Feast
Formula Feast bridges ion knowledge and formula writing. It walks us through the crossover rule step by step: identify the charges, swap the magnitudes to become subscripts, simplify if needed, and add brackets around polyatomic ions where the subscript exceeds one.
What makes this game valuable is the targeted feedback. When we make an error, the game provides instantaneous feedback. This matters because the most common mistakes (forgetting to simplify Mg₂O₂ to MgO, writing CaNO₃₂ instead of Ca(NO₃)₂) each reflect a different gap in understanding. Knowing which step failed helps us correct our reasoning.
Game 2: Ions Matchmaker
Before we can write a formula, we need to know our ions cold — their names, symbols, and charges. Ions Matchmaker drills exactly this, covering the full range of ions tested at O Level: simple cations like Fe²⁺ and Fe³⁺, simple anions like Cl⁻ and O²⁻, and polyatomic anions like SO₄²⁻, NO₃⁻, and CO₃²⁻.
The game format builds automaticity. The goal is to reach a point where we see “iron(III)” and immediately think Fe³⁺ — without having to reason it out. That instant recall is what makes the later steps of formula writing fast and error-free. If we need to double-check ion charges during revision, we are not ready for exam conditions; Ions Matchmaker fixes that.
Game 3: Formula Writing Challenge
The Formula Writing Challenge removes all scaffolding while expanding the scope to include covalent substances. We are given a compound name and must type the correct formula from memory. No guided steps, no hints — just the kind of independent recall the exam requires.
Progressive difficulty and immediate feedback on every answer make it effective for both consolidation and final exam preparation.
How to Use All Three Together
The games form a natural sequence:
Spend ten minutes on Formula Feast to practise the crossover rule. Make use of Ions Matchmaker until recall of every ion is automatic. Attempt Formula Writing Challenge under timed conditions.
Strong formula writing pays off across the entire the subject — in balancing equations, stoichiometry, ionic equations, and qualitative analysis. The time invested here is not time spent on one small topic. It is time spent getting better at the fundamentals which will serve us well.
