Examples of compounds with their formulas
A compound is a substance made of two or more elements chemically bonded in a fixed ratio, which its chemical formula shows. Compounds have properties that differ from those of their elements and can only be split into those elements by chemical reactions. Here are common compounds you meet at home, in your body and in the lab.
- Water (H₂O) — covers most of Earth's surface and makes up more than half of the human body.
- Carbon dioxide (CO₂) — the gas you breathe out, which plants use for photosynthesis.
- Sodium chloride (NaCl) — table salt, an ionic compound of sodium and chlorine.
- Glucose (C₆H₁₂O₆) — the sugar made by plants and used by your cells for energy.
- Sucrose (C₁₂H₂₂O₁₁) — ordinary table sugar, made from sugarcane or sugar beets.
- Ammonia (NH₃) — a sharp-smelling gas used to make fertilizers and some household cleaners.
- Methane (CH₄) — the main component of natural gas.
- Propane (C₃H₈) — fuel for gas grills and camping stoves, stored as a liquid under pressure.
- Sodium bicarbonate (NaHCO₃) — baking soda, which releases carbon dioxide in baking.
- Calcium carbonate (CaCO₃) — the main compound in limestone, marble, chalk and eggshells.
- Hydrogen chloride (HCl) — dissolves in water to form hydrochloric acid, which is found in stomach acid.
- Sulfuric acid (H₂SO₄) — a strong acid used in car batteries and to make fertilizers.
- Sodium hydroxide (NaOH) — lye, a strong base used in soap making and drain cleaners.
- Ethanol (C₂H₅OH) — the alcohol in alcoholic drinks, hand sanitizers and some fuels.
- Acetic acid (CH₃COOH) — gives vinegar its sour taste and sharp smell.
- Hydrogen peroxide (H₂O₂) — a disinfectant and bleach, usually sold as a 3% solution.
- Carbon monoxide (CO) — a toxic, colorless, odorless gas produced when fuels burn without enough oxygen.
- Iron(III) oxide (Fe₂O₃) — the main part of rust and of the iron ore hematite.
- Silicon dioxide (SiO₂) — quartz, the main component of most sand and of ordinary glass.
- Nitrous oxide (N₂O) — laughing gas, used by dentists to ease pain and anxiety and in whipped cream cans.
- Caffeine (C₈H₁₀N₄O₂) — the stimulant in coffee, tea and many soft drinks.
- Aspirin (C₉H₈O₄) — acetylsalicylic acid, a common pain reliever.
- Sodium hypochlorite (NaClO) — the active ingredient in household chlorine bleach.
- Magnesium hydroxide (Mg(OH)₂) — milk of magnesia, used as an antacid and laxative.
- Sodium fluoride (NaF) — added to many toothpastes to help prevent tooth decay.
Ionic and molecular compounds
Ionic compounds, such as sodium chloride and calcium carbonate, form when a metal transfers electrons to a nonmetal, creating ions held together in a crystal lattice. They are usually hard solids with high melting points. Molecular (covalent) compounds, such as water, carbon dioxide and glucose, form when nonmetal atoms share electrons. Many of them are gases or liquids at room temperature, or solids with fairly low melting points.
Compound or mixture?
A compound always has the same composition: every sample of pure water is about 11.2% hydrogen by mass. A mixture such as salt water can contain more or less of each part, and those parts keep their own properties.