
A weighted average mass of the atoms of an element; e.g. Atomic mass of Cl = 35.45, calculated from two isotopes: Cl35, Cl36 


Found by adding all the atomic masses of an element. e.g. water, H_{2}O: molecular mass = 18
Equation: 2(1) + 16 = 18



6.02 X 1023 items; can be anything: atoms, elephants, marshmallows. 


The number of atoms or formula units in x grams of an element or molecule, where x is the atomic or molecular mass. Always equal to 6.02 X 1023 

How many molecules in 0.5 moles of CuNO2? 


How many grams in 5 moles of ammonia (NH3)? 


How many moles in 50 grams of Hydrogen gas (H2)? 

