1) Moles

• A mole (mol) is a measure of the number of particles (atoms, ions or molecules) contained in a substance.
•  One mole of any substance (element or compound) contains the same number of particles - six hundred thousand billion billion or 6.02 x 1023.

  This value is known as the Avogadro constant.
• The mass of one mole of a substance is its relative atomic mass or relative formula mass in grams.