Friday, October 8, 2010

Naming + Writing forumlas for Ionic and Covalent Compounds

 Last class we reviewed material we first did in Grade 9 science. It's a fundamental part of Chemistry so make sure you know the stuff :)

Difference between Ionic and Compounds
* For covalent compounds, there is a special type called the Diatomic molecules. There are 7 of them (H2,O2,F2,Br2, N2, Cl2, I2). A way to remember them is by saying "I Bring Clay For Our New House".

Writing formulas for  Ionic Compounds
Basic → eg. Manganese (IV) Sulphide → Mn with a (+4) charge and Sulphur with a (-2) charge
- Simply switch the 2 subscript then you will have the answer
∴ Manganese (IV) Sulphide = Mn2S4 = MnS4
* You MUST simply the numbers if possible

Complex → eg. Ammonium Nitride =  (NH4)3N
- NH4 is Ammonium. You must put a bracket around it if there's another subscript followed behind.
 In other words, if there's no bracket, it will become NH43N. It's completely different and WRONG.

Naming Ionic Compounds
Basic →  eg. CaCl = Calcium Chloride
- Find the names from the periodic table that match with the symbols
* Remember the name of a compound always ends with "ide"
- Complex ions use the same method of naming. They just appear longer, doesn't necessary mean harder to name. eg. Cu2(NO3) = Copper (II) Nitrate

Ion with more than one charges eg. FeO = Iron (II) Oxide
- Iron can have charge (2+) or (3+)
- You must indicate which charge the ion has by using Roman numerals otherwise it may lead to confusion

Greek Prefixes (Please memorize them!)

* Be careful that #10 is "DECA"
   not "Deka" from the SI Prefixes


Naming Covalent Compounds
eg. CF4  → Carbon Tetraflouride   (Tetra = 4)
* If the first atom of the formula doesn't have a subscript, you don't need have to write "mono" for it. But if it's the second atom then you need it. eg. CO = Carbon Monoxide not Monocarbon Monoxide

Writing formulas for Covalent Compounds
eg. Diphosphorus Pentaoxide = P2O5   (Di = 2, Penta = 5)
- All you have to do is  match the prefix with the right number. Easy, isn't it? 

By Catherine 

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