Final answer:
A mole of any substance contains 6.022 × 1023 representative particles, known as Avogadro's number, and is the base unit of amount of substance in the SI system.
Step-by-step explanation:
A mole of any substance contains Avogadro's number (6.022 × 1023) of representative particles, such as atoms, molecules, ions, or electrons. The mole (symbol: mol) is the base unit of amount of substance in the International System of Units (SI), and it provides a bridge between the macroscopic world we observe and the atomic level we study in chemistry.
For instance, one mole of carbon-12 (12C) has a mass of exactly 12 grams, and it contains 6.022 × 1023 atoms of carbon. The same number of atoms would be found in a mole of any other element, although their mass would be different and equal to the atomic mass of the element in grams. Similarly, Avogadro's number is also used for molecules, such as 6.022 × 1023 molecules of water (H2O) making up one mole of water.