Define a mole and give an example​

A mole corresponds to the mass of a substance that contains 6.023 x 1023 particles of the substance. The mole is the SI unit for the amount of a substance. Its symbol is mol. By definition: 1 mol of carbon-12 has a mass of 12 grams and contains 6.022140857 x 1023 of carbon atoms (to 10 significant figures). Examples
1. Equations

When we write chemical equations, the quantities are assumed to be in moles. For example, in the following reaction one mole of bromine gains two moles of electrons to form two moles of bromide ions:

16- counting by fours