Question

What do you understand by the term "mole"? How many elementary units are in one mole of a substance?

Answer 1

A mole is the quantity of a substance containing Avogadro's number of elementary particles such as atoms, ions or molecules.
In one mole of a substance 6.023$\times$10²³ elementary units are present.
Alternatively, one mole is the amount of substance that contains as many elementary entities as the number of atoms present in 12 grams of C-12.
1 mole = 6.023$\times$10²³