1. Molar MassRe-Teach

2. Predicting Formulas Understand how to use oxidation numbers! Oxidation numbers are only used on ionic compounds. Ionic compounds are a metal+non-metal.

3. Oxidation Numbers IA is +1 IIA is +2 VIA is -2 VIIA is -1 The net charge needs to be “0”

4. Oxidation Numbers Let’s look at an example! Magnesium chloride Mg2+ + Cl- Criss cross the numbers and drop the charge! X + Y = 0 (x=2, Y=-1) How many x’s, y’s? MgCl2

5. Covalent Compounds Use prefixes to predict the compound. There are no oxidation numbers. Only for bonds with non-metals. Ex: Silicon Dioxide SiO2

6. Molar Mass Let’s first look at an ionic compound! Sodium Oxide Determine the oxidation numbers for both compounds. Now let’s predict the formula. Na2O

7. Molar Mass Na2O What does this formula tell us? 2 sodiums 1 oxygen

8. Molar Mass Refer to the periodic table for mass. Use the atomic mass, convert it to grams and this becomes your molar mass. Na=23g/mol O=16g/mol

9. Molar Mass Na2O You have 2 sodiums, 23gx2=46g You have 1 oxygen, 16gx1=16g Add 46g + 16g. The total molar mass is 62g.

10. Molar Mass Covalent compounds. Carbon Tetra-Chloride 1 carbon, 4 chlorines C=12g Cl=35gx4=140g CCl4=152g