1. The mole summary Relative atomic mass expressed in grams  1 mole
carbon-12 - the commonest natural carbon isotope, of mass 12. It is the basis for the accepted scale of atomic mass units.
Relative atomic mass expressed in grams  1 mole
1 mole of carbon has x 1023 carbon-12 atoms and you would have a mass of 12.01g
What would the mass of one carbon atom?
12.01g ÷ x 1023 = x10 -23g
Divide this number by 12
x10 -23g ÷ 12 = x 10-24g rougly speaking, this is the amu in grams
Multiply that number by Avagadro’s number (NA) i.e (x by a mole)
x 10-24g x x 1023 = g

2. How do we count atoms?
How does a bank count very large numbers of coins?
By measuring the total mass.

3. How do we count atoms? What do they need to know in order to do this?
The mass of a single atom .
Chemists count atoms in the same way, but we need to know how much an atom weighs – this is it’s R.A.M. (Relative atomic mass)

4. Calculate the mass (m) of each of the following:
1. 2 moles of iron [Fe]
mole of nitrogen [N2]
Calculate the number of moles (n) in :
1. 28 g of silicon [Si]
40 g of bromine [Br2]

5. Density Do these blocks have the same volume? Y/N
Do they have the same mass? Y/N
Do they have the same density? Y/N
Density is defined as the ratio between mass and volume or mass per unit volume. It is a measure of how much stuff an object has in a unit volume (cubic meter or cubic centimeter)

7. Sphere challenge
How many atoms are contained in a titanium sphere having a diameter of 6mm? The density of titanium is g/cm3.
Volume of a sphere

8. Solution hint Step 1 – calculate the size of a sphere.
Step 2 – Calculate the mass of Titanium.
Step 3 – Work out the number of moles of titanium you would have.
Step 4 – Calculate the number of atoms.