Elements and Compounds
· Elements are pure substances made up of only one type of atom.
· Elements cannot be broken down into simpler substances.
· Compounds are formed when two or more different elements chemically
· Compounds have properties different from the properties of the elements
that make them.
· Compounds are identified by chemical formulas.
· Some common compounds include water – H2O, salt – NaCl, and Carbon
Dioxide – CO2.
· A molecule is the smallest particle in a chemical element or compound that
has the chemical properties of that element or compound. Molecules are
made up of atoms that are held together by chemical bonds.
· Molecules can be made up of two like atoms (such as O2) or two different
types of atoms (such as H20).
· A chemical formula shows what elements a compound contains.
· Most substances found in nature are mixtures.
· Mixtures are substances that are mixed together but are NOT chemically
· Mixtures have no set ratio so they cannot be shown with a chemical
formula or symbol.