2. So far, we have learned how to take different elements and combine them together to make a compound. But there are some elements that have several oxidation states. For example, what is the formula for lead oxide? Pb has two oxidation states Pb +2 and Pb +4 Pb +2 O -2 PbO Pb +4 O -2 PbO 2 Which of the two is correct? BOTH are correct! Need a system to create a different name for each.

3. The stock system is only used when the first part of a compound (the positive one) has two or more positive oxidation states. Which of the following requires the stock system? CuO MgO LiNO 3 NO CaSO 4 Ni(NO 3 ) 2 ZnCO 3 Yes NO Yes NO Don’t worry about the negative ion. This system is used for the positive ion!

4. So how do I apply the stock system to these molecules? oxidation state is written as roman numerals In the stock system, we name the oxidation state that the first element is in. The oxidation state is written as roman numerals after the first element. Pb +2 O -2 PbO Pb +4 O -2 PbO 2 Pb is in the +2 state, so it is called Lead (II) oxide Pb is in the +4; state, so it is called Lead (IV) oxide

5. SnCl 2 The Cl must be in the -1 state, since Sn must be a positive oxidation state, Since there are two Cl’s, the Sn must be in the +2 oxidation state to cancel out the Cl’s -2 +2 Sn has 2 possible oxidation state; +2 and +4. Tin(II)Chloride +2= 0

6. Practice - All of the following compounds need the stock system. Determine the oxidation state of the cation (the first ion) and write out the name. CuNO 3 NiF 2 HgO Hg 2 O FeCl 3 NO 2 +1 Copper (I) nitrate +2 Nickel (II) fluoride -2+2 -2+2 Mercury (II) oxide -2+1 Mercury (I) oxide -2+2 -3 +3 Iron (III) chloride -2 -4 +4 Nitrogen (IV) oxide

7. If we are given a chemical name that uses the stock system, how do we write the formula? Example - What is the chemical formula for Copper (II) oxide? We know that the compound contains copper and oxygen Cu O And we know that oxygen must take a -2 oxidation state -2 Don’t have to look up copper. The (II) tells us that it is in the +2 state +2 So the formula for copper (II) oxide isCuO

8. Here’s another one What is the formula for Nickel (III) sulfate? NiSO 4 -2According to chart E!+3 Ni 2 (SO 4 ) 3 Now write out the formulas for the following. Nitrogen (II) chloride Iron (III) oxide Lead (IV) carbonate Copper (I) sulfate N +2 Cl -1 NCl 2 Fe +3 O -2 Fe 2 O 3 Pb +4 CO 3 -2 Pb(CO 3 ) 2 Cu +1 SO 4 -2 Cu 2 SO 4