AVOGADRO'S NUMBER

It is said Avogadro's number, from the name of its discovering Amedeo Avogadro (Tourin 1776-1856), the number constant number of molecules of a given substance contained in a mole of that substance. It is an universal constant and its value is:
N°_AV=6.022045*10²³molecole/mole.

In XIX century scientists found, from Avogadro's principle, 2g of H occuped 22.4L and they contained a certain number of molecules, but 16g of O₂ occuped the same volume and they occuped the same number of molecules. So the it was born the concept of mole: the amount of substance which occupes in the gasses a volum of 22.4L.

But if the considered element isn't a gas to find how many atoms are in a mole it needs considere a number of grams equal at the number of molecular weight.

From the definition of mole we can deduce between the number of particeld and the number of moles:N°_AVparticels ⇔1mol;; so N°_AV/1=N°_AVrepresents the number of particels which are equivalent at a mole;1/N°_AVrepresents the number of moles which are equivalent at a particel.