We might all have come across the number 6.0221415 × 1023 in our chemistry text books. It is called the Avogadro’s number in honor of the Italian scientist Avogadro who found it. In simple terms, it is referred to as a ‘mole’. A mole or Avogadro’s number is simply used by the chemists to measure the amount of a substance or count the particles of matter – atoms and molecules. Today Avogadro’s number(6.0221415 × 1023) has such a great importance that mole day is being celebrated every year by the chemists unofficially on 23rd October beginning from 6:02 AM to 6: 02 PM to make sense to Avogadro’s number.
We know that the nucleus of an atom makes up more than 99.9% of its mass. Electrons do not contribute anything to the mass of an atom which is measured in terms of atomic mass unit (amu). One amu is defined as 1/12th of the mass of one carbon atom (with 6 protons and 6 neutrons inside the nucleus). But as the chemists did not have a scale to measure different weights of different atoms, they wanted to find a relation between amu and grams. One amu was found to be equivalent to 1g/mol (or)
1 amu = 1/6.0221415× 1023 grams.