Elements, Compounds and Molecules What is a Compound? What is a Molecule? How can you tell how many?

Review Atoms are the building blocks of Elements Atoms of the same element will be similar in size, shape and in number of subatomic particles. An Element is a pure substance that CANNOT be broken down.

How can an Element be Represented? 1) Molecule: Is composed of a cluster of atoms A molecule’s atoms can be broken down into individual atoms during a chemical change.

How can an Element be Represented? 2) Compound A pure substance where the molecules are made of different kinds of atoms. Compounds can be broken down into simpler substances (i.e. ELEMENTS)

Household examples of Compounds: Table Salt - Sodium Chloride - NaCl Sugar - Sucrose, C6H12O6 Vinegar - Acetic Acid – AcOH Baking Soda - Sodium Bicarbonate - NaHCO3

What can Chemical Formulas tell us about Compounds and Elements? A Chemical Formula is: The combination of chemical symbols that indicate what elements make up a compound and the number of atoms of each element present. Example: H2O H=symbol for hydrogen, the number 2 indicates that there are 2 atoms of hydrogen O=symbol for oxygen, no value is shown, treated as 1

Mono, Di and Poly Element in compounds can be classified in 3 different ways: Monatomic Element: Only 1 element present Diatomic Element: 2 elements present Polyatomic Element: 3 or more.