Key Terms
* Compound: This is the most direct indicator. A compound is a substance formed when two or more different elements are chemically bonded together.
* Molecule: While not all molecules are compounds, a molecule *is* a group of two or more atoms held together by chemical bonds. Therefore, any compound is also a molecule.
* Chemical Formula: A compound will always have a specific chemical formula that represents the types and numbers of atoms in its molecule. For example, water (H₂O) has two hydrogen atoms and one oxygen atom.
* Fixed Ratio: The elements in a compound always combine in a fixed ratio by mass. For instance, table salt (NaCl) will always be 39.34% sodium and 60.66% chlorine by mass.
* New Properties: Compounds have properties that are different from the elements that compose them. For example, sodium (Na) is a highly reactive metal, and chlorine (Cl) is a poisonous gas, but together they form the familiar table salt (NaCl), which is a white, crystalline solid.
Additional Considerations:
* Mixture vs. Compound: A mixture is a combination of substances where each substance retains its individual properties. A compound is a new substance with unique properties.
* Ionic Compounds: These compounds are formed by the electrostatic attraction between oppositely charged ions.
* Covalent Compounds: These compounds are formed by the sharing of electrons between atoms.
Examples:
* Water (H₂O) is a compound made of hydrogen and oxygen.
* Carbon Dioxide (CO₂) is a compound made of carbon and oxygen.
* Sodium Chloride (NaCl) is a compound made of sodium and chlorine.
Let me know if you have any more questions about chemical compounds!
