One mole (mol) contains exactly 6.02214076 × 1023 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number. The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles.
When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
The SI unit of concentration (of amount of substance) is the mole per cubic meter (mol/m3).
This comic book-style video animation series has been developed to help middle school students learn about the 7 SI base measurement units. Able to sniff out and count the atoms of every element, the Mole is the king of chemistry. Equal to about 600 sextillion (that's a 6 followed by 23 zeros!), a mole is a shorthand way to talk about huge numbers, especially of tiny things.