Transcript The Mole

The Mole
the link between the
macroscopic gram and the
nanoscale  our “scale up”
The Mole
number of atoms needed to have
atomic mass in grams
6.02 x 1023
Using the Mole to Scale Up to
Grams
• When I have 6.02 x 1023 protons or
neutrons (nucleons), I will have a mass of
about 1 gram
• In class, discuss Carbon
• Consider other atoms
– Suppose we have 1 mole (6.02 x 1023 Na -23
atoms)
– Suppose we have 1 mole (6.02 x 1023 F - 19
atoms)
Using the Mole to Scale Up to
Grams: Na - 23
this is 1 mol of Na atoms
 23 nucleons

6.02 x 10 Na atom s
 Na atom 


23
= (6.02 x 1023 x 23) nucleons
= (23) x (6.02 x 1023 nucleons)
23
x
1g
= 23 g
This is atomic
mass of Na - 23
(but in grams)
Using the Mole to Scale Up to
Grams
• So, when I have 1 mole (or 6.02 x 1023
atoms) of Na -23, I must have 23 g !!
Using the Mole to Scale Up to
Grams: F - 19
this is 1 mol of F atoms
 19 nucleons

6.02 x 10 F atom s
 F atom 


23
= (6.02 x 1023 x 19) nucleons
= (19) x (6.02 x 1023 nucleons)
19
x
1g
= 19 g
This is atomic
mass of F - 19
(but in grams)
Using the Mole to Scale Up to
Grams
• So, when I have 1 mole (or 6.02 x 1023 atoms)
of F - 19, I must have 19 g !!
• Based on this scale up, whenever I have one
mole of atoms of an element, I will have the
atomic mass of that element in GRAMS
→ if I have 1 mole of He atoms, I will have 4 g of He
→ if I have 1 mole of Cr atoms, I will have 52 g of Cr
→ etc.
Using the Mole
• The link between macroscopic grams and
nanoscale number of particles!
• If I had 0.750 mol of Pb,
– How many grams of Pb must I have?
– How many atoms of Pb must I have?