1. Compounds

2. Review:  Element: -pure substance that cannot be broken down into a simpler substance by ordinary chemical changes. -consists of atoms of only one type. -Combine in specific ways to form new substances due to the electron levels. -The combination forms bonds between the atoms, producing a compound.

3. Properties of compounds:  depends on which atoms it contains  how the atoms are arranged  often very different from the elements that make them Examples: water, H 2 O salt, NaCl salt, NaCl

4. Compounds continued…  Compounds always contain atoms of elements in a specific ratio. Example: Ammonia, 3:1, hydrogen to nitrogen Hydrazoic acid, 1:3, hydrogen to nitrogen Methane, 1:4, carbon to hydrogen Propane, 3:8, carbon to hydrogen

5. Different Compounds:  The same elements can form different compounds. Example: Water, H 2 O Hydrogen peroxide, H 2 O 2

6. Chemical Formulas:  An expression that shows the number and types of atoms joined in a compound. Example: Carbon dioxide, CO 2, 1:2 ratio Carbon monoxide, CO, 1:1 ratio Glucose, C 6 H 12 O 6, 6:12:6 or 1:2:1 ratio

7. Chemical Formulas con’t…  Note: If the chemical formula does NOT have a subscript in it, it is understood as a 1:1 ratio. Example:NaCl, HCl