MOLE - amount of substance which is 6.02 x 10 raise to the 23rd particles.

a. Atom - charged element.
b. Molecule - covalent
c. Ion pair - ionic

Amadeo Avogadro
 - Avogadro's no. - 6.02 x 10 raise to the 23rd  or "N"

Examples :
 1 mol Na - 6.02 x 10 raise to the 23rd  Na atoms
 1 mol H2O -6.02 x 10 raise to the 23rd  H2O molecules
 1mol NaCl - 6.02 x 10 raise to the 23rd  NaCl Ion pairs