Common compounds and their formulas
Most searches here are one of a few dozen everyday compounds. This table covers the ones people look up by name or by formula.
| Common name | Formula | Chemical name |
|---|---|---|
| Table salt | NaCl | Sodium chloride |
| Water | H₂O | Water (dihydrogen monoxide) |
| Baking soda | NaHCO₃ | Sodium bicarbonate |
| Dry ice / CO₂ | CO₂ | Carbon dioxide |
| Lye / caustic soda | NaOH | Sodium hydroxide |
| Limestone / chalk | CaCO₃ | Calcium carbonate |
| Battery acid | H₂SO₄ | Sulfuric acid |
| Muriatic acid | HCl | Hydrochloric acid |
| Ammonia | NH₃ | Ammonia (nitrogen trihydride) |
| Blue vitriol | CuSO₄ | Copper(II) sulfate |
| Natural gas (main part) | CH₄ | Methane |
| Grape sugar / dextrose | C₆H₁₂O₆ | Glucose |
The three naming patterns cover almost everything
- Metal + nonmetal (ionic). Metal name first, nonmetal takes an ide ending: NaCl is sodium chloride, MgO is magnesium oxide.
- Nonmetal + nonmetal (covalent). Add Greek prefixes for the atom counts and end in ide: CO₂ is carbon dioxide, N₂O₄ is dinitrogen tetroxide. The first element skips "mono".
- Hydrogen + a nonmetal or anion (acid). A plain nonmetal gives "hydro__ic acid" (HCl is hydrochloric acid); an ate anion gives "__ic acid" (H₂SO₄ is sulfuric acid), an ite anion gives "__ous acid".
Variable-charge metals need a Roman numeral
Iron, copper and tin can carry more than one charge, so "iron chloride" is ambiguous. The name states the charge in brackets so the formula is unmistakable.
The Roman numeral is the charge on the metal ion, not the number of chlorine atoms. Fixed-charge metals such as sodium, potassium and calcium never need one.
Common questions
What is the formula for table salt?
Table salt is sodium chloride, NaCl. One sodium atom bonds with one chlorine atom, so the charges balance to zero.
Why is NaCl called sodium chloride and not sodium chlorine?
When a nonmetal becomes the negative ion in an ionic compound, its name takes the ide ending: chlorine becomes chloride, oxygen becomes oxide. The metal keeps its own name and goes first.
What is the difference between a chemical formula and a chemical name?
The formula is the shorthand, like H2SO4. The name is the words, sulfuric acid. The formula tells you which elements and how many atoms of each; the name tells you what kind of compound it is.
