The mole (abbreviation, mol) is the Standard International ( SI ) unit of material quantity. One mole is the number of atom s in precisely 12 thousandths of a kilogram (0.012 kg) of C-12, the most common naturally-occurring isotope of the element carbon. This number is equal to approximately 6.022169 x 10 23 , and is also called the Avogadro constant.
The mole is the only fundamental SI unit that is dimensionless. That means it represents a simple numerical quantity or value; it is a term similar in nature to "dozen" (meaning 12) or "gross" (meaning 144). But 1 mol is, unlike a dozen or a gross, an incomprehensibly large number. Written out in decimal form, it appears as 602,216,900,000,000,000,000,000. Envision a huge cubical box measuring about 84 kilometers (84 km) on each edge. Then imagine that box being neatly packed full of sand-grain-size cubes measuring a millimeter (1 mm) on an edge. If this were done, the box would contain roughly 1 mol of cubes.
The mole is of interest primarily to chemists and physicists. Sometimes, larger or smaller units are defined by attaching power-of-10 prefix multiplier s. For example, a kilomole (1 kmol) is 10 3 mol, or approximately 6.022169 x 10 26 , and a millimole (1 mmol) is 10 -3 mol, or approximately 6.022169 x 10 20 .