1. Chemical Formulas
Mr. Dunnum

2. Chemical Formulas represent compounds.

3. Interpreting Chemical Formulas
Coefficient
Number that is placed in front of a chemical formula or a symbol in a chemical equation that indicates the number of moles or molecules of this substance involved in the reaction
Subscript
Number placed to the lower right of a chemical symbol to indicate the number of atoms of the element in the compound.

4. Interpreting Chemical Formulas
2Na2O
2 = coefficient= 2 moles of this element
Number of atoms for each element coefficient * subscript
If you do not see a subscript, it is understood to be 1
Na = 2*2 = 4
O = 2*1 = 2
Total # of atoms = 4+2 = 6

5. Interpreting Chemical Formulas
3Ba3(PO4)2
Ba = 3*3 = 9
P = 3* (2*1) = 3*2 = 6
O = 3* (4*2) = 3*8 = 24
Total # of atoms = = 39
When you have parenthesis, you must multiply the subscript on the outside of the parenthesis by every subscript on the inside of the parenthesis before you multiply by the coefficient

6. Writing Chemical Formulas
You need to know the chemical symbol for the element
You need to know the element’s oxidation number
Oxidation number is the number of valence electrons an element gains, loses, or shares during bonding
For metals, the oxidation number is positive
For nonmetals, the oxidation number is negative
Column 14 is considered an exception; its oxidation number is +/-4 depending on what it is bonding with