What is Avogadro's number

The fixed value of the amount of particles, atoms or molecules present in One Mole of any substance which was calculated by Amedeo Avogadro, an Italian Scientist who is most noted his contribution to the molecular physics and He was also the Count of Quaregna and Cerreto.

Avogadro's Number:

• The amount of atoms, molecules or particles present One Mole of any substance is called Avogadro's Number.
• The value of Avogadro's Number is: 6.02x10²³
• Avogadro's Number is denoted by or The symbol of Avogadro's Number is: N_A

Example:

1 mole of H²O contains 6.02x10²³ molecules of water
1 mole of H contains 6.02x10²³ molecules of Hydrogen
1 mole of NaCl contains 6.02x10²³ atoms of Na + 6.02x10²³ atoms of Cl

Other Important Links:
What is Mole?
Who was Amedeo Carlo Avogadro

References: Wikipedia