ATOMS AND MOLES

1) For monoatomic elements:
a molecule= an atom

2) Diatomic elements
A MOLECULE: AN ATOM:
Cl2. Cl

3) Molecules of Compounds
2 Hydrogen atoms and 1 oxygen atom create water which is one molecule.

FORMULA FOR ATOMS AMD MOLES
6.02x10^23molecules/ 1 mol OR 1 mol/ 6.02x10^23

Examples:
how many molecules in 0.25mol of CO2?
0.25mol x 6.02x10^23 molecules= 1.51x10^23

How many moles in 5.1772x10^24 molecules of H2O?
5.1772x10^24 molecules/ 6.02x10^23= 8.6mol

For more practice here is a printable practice worksheet.
www.emp.byui.edu/PECKK/chem105/molsheet.htm