1. ATOMIC AND MOLAR MASS

2. Atomic Mass 2  Considers mass numbers of all isotopes  Natural abundance  Weighted average

3. Calculating Atomic Mass 3 9.25%221210Ne-22 or 0.27%211110Ne-21 or 90.48%2010 Ne-20 or Percent Natural Abundance A, Mass Number Number of Neutrons Number of ProtonsSymbol

4. Practicing atomic mass 4  Practice—Ga–69 with mass 68.9256 amu and abundance of 60.11% and Ga–71 with mass 70.9247 amu and abundance of 39.89%. Calculate the atomic mass of gallium.

5. Counting atoms by moles  The unit mole is used by chemists to count atoms.  There are 6.022 x 10 23 particles in one mole  6.022 x 10 23 particles = 1 mole  Avogadro’s number  Notice particles is broad term  Atoms, ions, molecules, formula units  Value of mole is number of atoms in exactly 12 g of pure carbon-12  Base unit that can convert amongst other units in chemistry 5

6. Converting particles to moles using Avogadro’s number- practice 6 Determine conversion factors Put given over 1 Whatever unit is on top needs to be on bottom of next Equivalent to unit from conversion factor goes on top Multiply top divide bottom Determine the number of moles in 1.29 x 10 24 hydrogen atoms in HF

7. Converting particles to moles using Avogadro’s number- practice 7 Determine conversion factors Put given over 1 Whatever unit is on top needs to be on bottom of next Equivalent to unit from conversion factor goes on top Multiply top divide bottom Determine the number of Hydrogen atoms in 3.14 mol of H 2 O

8. Converting particles to moles using Avogadro’s number- practice 8 Determine conversion factors Put given over 1 Whatever unit is on top needs to be on bottom of next Equivalent to unit from conversion factor goes on top Multiply top divide bottom Determine the number of molecules in 4.90 mol of Al 2 O 3

9. Molar mass  Mass of 6.022 x 10 23 particles  So, if we were able to place 6.022 x10 23 atoms of copper it would way, on average, 63.55g. 9

10. Practice using molar masses 10 Determine conversion factors Put given over 1 Whatever unit is on top needs to be on bottom of next Equivalent to unit from conversion factor goes on top Multiply top divide bottom How many grams of copper are in 0.88 moles?

11. Practice using molar masses 11 Determine conversion factors Put given over 1 Whatever unit is on top needs to be on bottom of next Equivalent to unit from conversion factor goes on top Multiply top divide bottom How many grams of copper are in 0.88 moles?

12. Practice using molar masses 12 Determine conversion factors Put given over 1 Whatever unit is on top needs to be on bottom of next Equivalent to unit from conversion factor goes on top Multiply top divide bottom How many moles of aluminum are in 43.7g?

13. Practice using molar masses 13 Determine conversion factors Put given over 1 Whatever unit is on top needs to be on bottom of next Equivalent to unit from conversion factor goes on top Multiply top divide bottom How many grams of H 2 0 are in 5.34 x10 30 molecules?