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Graphite with AFM showing all atoms within the hexagonal graphite unit cells. Image size 2×2 nm2.

Graphite with AFM showing all atoms within the hexagonal graphite unit cells. Image size 2×2 nm2. STM image (7 nm x 7 nm) of a single zigzag chain of cesium atoms (red) on a gallium-arsenside surface (blue) Photo courtesy  National Institute of Standards and Technology (NIST. 77 pm resolution.

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Graphite with AFM showing all atoms within the hexagonal graphite unit cells. Image size 2×2 nm2.

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  1. Graphite with AFM showing all atoms within the hexagonal graphite unit cells. Image size 2×2 nm2. STM image (7 nm x 7 nm) of a single zigzag chain of cesium atoms (red) on a gallium-arsenside surface (blue) Photo courtesy National Institute of Standards and Technology (NIST 77 pm resolution. Subatomic structures are visible within single tungsten atoms. Image size 500 × 500 pm2

  2. Using Mass to Count Things • Atoms are so tiny it is impossible to count number of atoms in even 1 gram of matter • We use mass to “count” atoms

  3. Counting by mass • a pile of nails weighs 1227 g • one nail has mass of 0.450 grams • How many nails are in pile? 1227g_____ = 2726.6 nails 0.450 g per nail

  4. What is a mole? No, not this kind of mole!

  5. The MOLE • Unit used to “count” numbers of atoms • Count-by-mass technique • Defined as # of atoms in 12.0 grams of C-12 • This is the STANDARD! • 12.0 g of C-12 has 6.0221415 X 1023 atoms

  6. Just how big is a mole? Mole movie

  7. The MOLE • 1 mole of any element has 6.02 X 1023 particles • This is a really big number – It’s so big because atoms are really small!

  8. 6.02 X 1023 = Avogadro’s Number • One mole of water = 6.02 X 1023 water molecules • One mole of gorillas = 6.02 X 1023 gorillas • One mole of He atoms = 6.02 X 1023 He atoms • One mole of anything = 6.02 X 1023 of that thing

  9. Similar Words • Pair: 1 pair shoelaces = 2 shoelaces • Dozen: 1 dozen oranges = 12 oranges • Gross: 1 gross spider rings = 144 rings • Ream: 1 ream paper = 500 sheets of paper • Mole: 1 mole Na atoms = 6.02 X 1023 Na atoms

  10. 0.5 mole of C-12 = 6.0 grams of C-12 = 3.01 X 1023 atoms of C-12 Equalities • 1 mole of C-12 = • 12.0 grams of C-12 = • 6.02 X 1023 atoms of C-12

  11. 0.25 mole of C-12 = 3.0 grams of C-12 = 1.50 X 1023 atoms of C-12 Equalities • 1 mole of C-12 = • 12.0 grams of C-12 = • 6.02 X 1023 atoms of C-12

  12. 2 moles of C-12 = 24.0 grams of C-12 = 12.04 X 1023 atoms of C-12 = 1.204 X 1024 atoms of C-12 How does this help with other elements? Equalities • 1 mole of C-12 = • 12.0 grams of C-12 = • 6.02 X 1023 atoms of C-12

  13. Molar mass for any element: • molar mass of any element: • take atomic mass and replace amu with grams • 1 mole Ne = 20.179 g = 6.02 X 1023 atoms • 1 mole Ar = 39.948 g = 6.02 X 1023 atoms • 1 mole Kr = 83.80 g = 6.02 X 1023 atoms

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