Answer:
Explanation:
Substance are consist of very large number of atoms, ions , molecules etc.
They can not be count in a simple way. Scientist used Avogadro number to express the large number of atoms, ions, molecules.
Avogadro number:
It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.
The number 6.022 × 10²³ is called Avogadro number.
For example,
18 g of water = 1 mole = 6.022 × 10²³ molecules of water
1.008 g of hydrogen = 1 mole = 6.022 × 10²³ atoms of hydrogen
96.06 g of SO₄²⁻ ion = 1 mole of SO₄²⁻ ion = 6.022 × 10²³ ions of SO₄²⁻
