# Avogadro's Number

## Definition - What does Avogadro's Number mean?

Avogadro's Number is the number of atoms or molecules that are contained in a unit mole of a substance. Since this value remains constant for all the elements, it is also known as Avogadro constant. It is generally represented as the number of particles that are contained in one mole. Avogadro's number is a dimensionless quantity which provides the relation between other physical constants and properties.

## Petropedia explains Avogadro's Number

Avogadro's number is named after an Italian Scientist, Amedeo Avogadro in the 19^{th} Century. As per his theory, at certain pressure and temperature conditions, the volume of gas is proportional to the number of molecules in the gas irrespective of the nature of gas. In the international units system, Avogadro's number is represented by the symbol “N_{A }or L”. For example, one gram of hydrogen element is written as ^{1}H or simply H. This one is a representation that a hydrogen element has only one isotope whose atomic mass will be 6.022 x 10^23 hydrogen atoms. Similarly, carbon-12 has 12 grams of isotopes and is written as ^{12}C. This has 12 as the mass number and atomic number is 6 has same number of carbon atoms as 6.022 x 10^23.