2. 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

3. 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

4. Counting by mass a pile of nails weighs 1227 g
one nail has mass of grams
how many nails are in pile?
1227g_____ = nails
0.450 g per nail

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

6. 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 X 1023 atoms

7. Just how big
is a mole?
Mole movie

8. 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!

9. 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

10. 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

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

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

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

15. molar mass for any element:
molar mass of any element:
take atomic mass and replace amu with grams
1 mole Ne = g = 6.02 X 1023 atoms
1 mole Ar = g = 6.02 X 1023 atoms
1 mole Kr = g = 6.02 X 1023 atoms