1. CH. 3.4 Counting Atoms

2. ATOMIC MASS  Atoms are really small and have really small masses  Cu atoms have average mass of 1.0552 x 10 -25 kg  Special unit created for atoms called atomic mass unit (amu) Copper-63 is 62.940 amu Copper-65 is 64.928 amu Periodic table says 63.546 – this is the average of all the isotopes

3. THE MOLE!  Mole (mol): The # of atoms in exactly 12 grams of carbon-12 (How they decided on the number) 6.022 1367 x 10 23 atoms – Avogadro’s number MEMORIZE 6.022 x 10 23  Why do we do this? It’s like saying 1 dozen instead of 12 eggs Grouping things together to making counting easier

4. THE MOLE  Molar mass is the mass of 1 mole of an element  Same as the atomic mass number on the periodic table But atomic mass is really small and a mole is really big! Atomic mass is the # followed by units amu Molar mass is the # followed by units g/mol (grams per mol)

5. MOLAR MASS  Moving forward, we will stick to molar mass …and not really use atomic mass

6. CONVERTING MOLES, MASS, AND PARTICLES – OH MY!  Picket fence time!! 6.022 x 10 23  Mass  Molar Mass  Moles  Avogadro’s number  Particles (atoms)

7. PRACTICE!  Determine the mass of 3.50 mol of copper  3.50 mol63.546 g=222 g 1 mol

8. YOUR TURN  What is the mass in grams of 0.0050 mol of uranium?  Calculate the number of moles of 0.850 g of hydrogen atoms.

9. YOUR TURN  What is the mass in grams of 0.0050 mol of uranium? 1.2 g  Calculate the number of moles of 0.85 g of hydrogen atoms. 0.84 mol

10. PRACTICE!  Determine the number of atoms in 0.30 mol of fluorine atoms  0.30 mol6.022 x 10 23 atoms=1.8 x 10 23 atoms 1 mol

11. YOUR TURN!  How many atoms are in 0.70 mol of iron?  How many moles of silver are represented by 2.888 x 10 23 atoms?

12. YOUR TURN!  How many atoms are in 0.70 mol of iron? 4.2 x 10 23 atoms  How many moles of silver are represented by 2.888 x 10 23 atoms? 0.4796 mol

13. PRACTICE!  Determine the number of atoms in 10.0 g of sodium atoms  10.0 g1 mol 6.022 x 10 23 atoms= 2.62 x 10 23 atoms 22.990 g 1 mol

14. YOUR TURN!  Determine the number of atoms in 5.05 g of sulfur atoms.  Determine the mass of 3.56 x 10 24 phosphorous atoms.

15. YOUR TURN!  Determine the number of atoms in 5.05 g of sulfur atoms. 9.49 x 10 22 atoms  Determine the mass of 3.56 x 10 24 phosphorous atoms. 183 g of phosphorous atoms