Elements & compounds

Chemist classify pure substances based on the particles they are made of. Pure Substances are classified as Elements or Compounds ELEMENTS: A pure substance that cannot be broken down into simpler substances 109 elements have been isolated and identified, 91 are naturally occurring Elements are identified by their name, symbol and atomic number

Examples: Elements are the building blocks of all substances. A pure substance composed of two or more different elements in a fixed bond is called a Compound They can be broken into elements by chemical means Examples: Name: Hydrogen, Symbol: H, atomic #: 1 Name: Water, Symbol: H2O