Compound
Definition and meaning of Compound in chemistry.
A compound is a pure substance formed when two or more different elements combine chemically in a fixed ratio, held together by chemical bonds.
In more detail
Because the elements are chemically bonded rather than just mixed, a compound has properties distinct from its constituent elements and can only be separated back into elements by a chemical reaction, not by physical means like filtering or evaporation. Every sample of a given compound has the same fixed elemental composition and mass ratio, a principle known as the law of constant (or definite) proportions. Compounds are classified as ionic (formed by transfer of electrons between metals and nonmetals) or covalent/molecular (formed by sharing of electrons, typically between nonmetals).
Key facts
| Formula example | H2O (water) |
|---|---|
| Bond types | Ionic or covalent |
| Composition | Fixed ratio by mass (law of constant proportions) |
| Field | General Chemistry |
Water (H2O) is a compound in which two hydrogen atoms bond covalently to one oxygen atom; unlike the gases hydrogen and oxygen, water is a liquid at room temperature with completely different chemical behavior.
Frequently asked questions
What is the difference between a compound and a mixture?
A compound's components are chemically bonded in a fixed ratio and require a chemical reaction to separate, while a mixture's components are only physically combined, can vary in proportion, and can be separated by physical methods.
Is table salt a compound?
Yes, sodium chloride (NaCl) is an ionic compound formed when sodium and chlorine atoms combine in a 1:1 ratio.