Mole | Definition, Unit, Symbol and Examples|

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Mole is one of the seven basic physical quantities. It is used to measure quantity of a chemical substance in term of numbers of elementary particles - elementary particles of a chemical substance can be atoms, molecules, ions, formula units etc - just like one dozen of any thing has  12 items of that thing. 

1 mole of any substance= 6.022x10^23 elementary particles/mol.

Like
 1 dozen of any thing= 12 items/dozen.

DEFINITION
 A mole of any substance has exactly 6.022140766x10^23 elementary particles of given substance.This number is usually written in round off as 6.022x10^23.This number is known as Avogadro's number. Symbol used for Avogadro's number is NA.

SYMBOL & UNIT
Symbol designated for mole is "n" and its unit is "mol".

EXAMPLES
1 mole of sodium(Na) = 6.022x 10^23 atoms/mol.
1 mole of water(H2O) = 6.022x 10^23 molecules/mol.
1 mole of sodium ions(Na+) = 6.022x10^23 ions/mol.
1 mole of sodium chloride(NaCl) = 6.022x10^23 formula units/mol.

NOTE
In above examples elementary particles are
  •  In 1st example sodium is an elemental substance, its elementary particle is atom.
  • In 2nd example water is molecular compound, it's elementary particle is molecule.
  • In  3rd example, sodium ion is an ionic species, it's elementary particle is an ion.
  • In the 4th example, sodium chloride is an ionic compound its elementary particle is the formula unit.

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