The Mole

The mole, represented or abbreviated by the lowercase non-italicized English letters mol, is the standard unit of material capacity. It is also termed as Avogadro's number and is a big number, around 6.022169 x 10²³. This is the number of atoms in exactly 0.012 kg of carbon-12, the most general isotope of elemental carbon with 6 protons and 6 neutrons in the nucleus.

The mole occurs naturally in the physical world, particularly in chemistry. It is one of those strange numbers for which nature seems to have reserved a particular place. Or else, scientists surely would have preferred a round number like 1,000, or might be even 12 (i.e., one dozen).