Grade 10 · Theory
Names and formulae
Matter and classification · about 3 min
Visual overview: Names and formulae1 MIN READ
2 study sections · pause after each one and recall the key ideaChemistry has a precise naming system so that a formula tells you exactly what a substance contains.
Key points- Metal + non-metal gives an ionic compound: the metal is named first, the non-metal ends in -ide (NaCl, sodium chloride).
- Polyatomic ions keep their names (SO₄²⁻ sulphate, NO₃⁻ nitrate, CO₃²⁻ carbonate).
- Balance the charges so the compound is neutral: Al³⁺ and O²⁻ give Al₂O₃.
- Prefixes name covalent compounds: CO₂ is carbon dioxide, N₂O₄ dinitrogen tetroxide.
- Ion — a charged atom or group of atoms.
- Valency — the combining power of an atom.
EXAM TIP
learn the common polyatomic ions with their charges — most formula-writing marks depend on them.