Elements: Find the element on the periodic table. The number below the element symbol is the atomic mass. This number shows how many grams (g) are in each mole (mol) of that element. To convert g/mol to g, divide that number by Avogadro's Constant (approximately 6.022 x 10^23).
Molecular Compounds: To find the average mass (or molecular mass) in g/mol, add the atomic masses of each molecular atom. The atomic masses can be found below each element symbol on the periodic table. To convert g/mol to g, divide that number by Avogadro's Constant.
Ionic Compounds: Find the formula mass by adding the atomic masses of each atom. The atomic masses can be found below each element symbol on the periodic table. To find the molar mass of an ionic compound, multiply the atomic mass by the grams you have of that compound. To convert g/mol to g, divide that number by Avogadro's Constant.