Names that map to formulas
Chemical names tell you which atoms are in a compound and how they balance. Learn three rule sets — one for ionic, one for covalent, one for acids — and you can decode (or write) most names you meet.
Ionic compounds (metal + nonmetal)
Cation first, anion second. Drop the anion ending and add -ide for monoatomic anions: Na + Cl → NaCl, sodium chloride. Polyatomic anions keep their own name: CaSO₄, calcium sulfate.
Stock system (variable charge)
Transition metals can take more than one charge. Add a roman numeral after the metal name: FeCl₂ → iron(II) chloride; FeCl₃ → iron(III) chloride.
Covalent (nonmetal + nonmetal)
Use Greek prefixes — mono-, di-, tri-, tetra-, penta-... Drop "mono-" on the first element. CO → carbon monoxide; N₂O₄ → dinitrogen tetroxide.
Acids
Binary (no oxygen): hydro-X-ic acid. HCl(aq) → hydrochloric acid. Oxyacid with -ate anion: X-ic acid; with -ite: X-ous acid. HNO₃ → nitric, HNO₂ → nitrous.
Greek prefixes for covalent compounds
Hands-on tools
Convert in either direction; drill the polyatomic ions until they’re second nature.
Formula → name
Type a chemical formula. Works for binary ionic, transition-metal compounds with polyatomic ions, and binary covalent.
Quick try:
Name → formula
Type a compound name. Use lowercase; for variable-charge metals include the roman numeral as "iron(III)".
Quick try:
Polyatomic ion drill
Click "next" to challenge yourself; the back of the card has formula, name and charge.
Polyatomic table — tap a cell for detail
Common cations & anions
Reference table — click a row for compounds containing it.
Cations
Anions
Quiz
Flashcards
Tap a card to flip. ← / → keys to navigate.
Daily challenge
Five compounds to name. Same set worldwide, refreshes at midnight UTC.
For teachers
Print-ready worksheet, answer key, teaching tips and standards alignment.
Teaching tips
Standards alignment
Reference
Common compounds
Glossary
Photo gallery — common compounds
Images sourced from Wikipedia.