aslaam alykum,

The mole is a large number, aprox 600 000 000 000 000 000 000 000

that = 1g of hydrogen
=12g of carbon
24g of magnesium

Therefore the relative atomic mass of an element can be expressed in grams contains ONE mole of atoms. This means that the number of atoms of an element can be worked out by weighing.

Calculations can be done by simple equations,

Moles of atoms = mass/RAM

Examples:
1) how many moles of atoms are there in 72g of Mg?
(RAM of mg= 24)

Write down the formula Moles= mass/RAM
rearang if necessary (not needed)
Subsitute the numbers moles= 72g/24
Write the answer and units moles = 3moles

2) what is the mass of 0.1 moles of carbon atoms?
(RAM of carbon = 12)
Write formula
rearange mass= moles * RAM
sub numbers mass= 0.1 * 12