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Writing Formulas
Classification of Matter
Naming Compounds
Writing Formulas
The Periodic Table
Atomic Structure
Mole Calculations

Don't Forget About Formulas!

There are different ways to write different formulas.
Ionic Compounds
Calcium & Nitrogen
1. Identify the two elements
Ca & N
2. Identify the charges of the two elements.
Ca + 2    N -3
3. Make sure the charges balance by multiplying them together if they do not add up to zero.
Ca 2(3)  N -3(2)
=Ca3 N2
Ionic Compounds with Polyatomic Ions
Iron III & Sulfate
1. Identify the 2 elements.
Fe & SO4
2. Identify the charges. Make sure you don't mix up the charge with the number of elements!
Fe +3    (SO4)-2
3. Balane the charges. The charge goes on the OUTSIDE of the parenthesese.
Covalent Compounds
Dicalcium Heptachloride
1. Identify the elements.
Ca & Cl
2. Identify the NUMBER in each molecule.
Ca has 2 (DIcalcium)  and Cl has 7 (HEPTAchloride)
3. Write that number behind the element's symbol.

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