1. Elements, Compounds and chemical formulas

2. Review: What is a Element?
Element - a pure substance that is made up ONE type of atom.
Note: If there is more than one atom of the SAME element, it is called a “molecule” – It is NOT a compound.

3. Review: What is a compound?
Compound - a pure substance that is made up of 2 or more DIFFERENT types of atoms (elements).
When compounds form, a chemical reaction has occurred.

4. What are chemical Formulas?
The formula of a compound identifies the elements in the compound and the ratios in which their atoms are present.
How many atoms of each element are present in each of these compounds 

5. WHY do Elements form Compounds?
… To become more stable!
Example:
Na is flammable and Cl2 is a toxic gas.
They combine to form NaCl (Sodium Chloride)
NaCl is a very stable compound that is neither flammable nor toxic

6. What if a Compound is unstable?
If compounds are unstable, then they will break down to form stable elements.
Example:
H2O2 (Hydrogen Peroxide) will break down into Water (H2O) and release the extra Oxygen atom as a gas.

7. Magnesium Hydroxide – Mg(OH)2 Mg = 1 O = 2 H = 2
Aluminum Oxide – Al2O3
Al = O = 3
Calcium Bromide – CaBr2
Ca = 1 Br = 2
Sulfuric Acid – H2SO4
H = S = 1 O = 4
Magnesium Hydroxide – Mg(OH)2
Mg = 1 O = H = 2
Ammonium Phosphate – (NH4)3PO4
N = 3 H = P = 1 O = 4
Iron Sulfate – Fe2(SO4)3
Fe = S = O = 12
Chemical Formulas
*When a subscript is outside of a parenthesis, then it multiplies to both of the elements.