The August 9, 1776, in the Italian city of Turin, the birth of Amedeo Avogadro. This chemist and physicist who died at 79 years of age went down in history for his contributions to the field of Sciences: in fact, today we know by name a law or principle and a number or constant.

It must be established that Amadeo gave an important impetus to the study of atomic theory and that he developed his famous law based on other theories such as those created by Gay-Lussac and by John Dalton.

It is interesting to know that, at first, when he made his work and his aforementioned law known, it did not have the support or interest of most of the scientific community. It was simply ignored and that, shortly after, other scientists came to support their discoveries with others of their own that they had carried out on their own.

It took a long time afterwards for his work to be recognized. Specifically, that happened when works such as those by Williamson, Gerhardt or Laurent were presented that made it clear that Amedeo was right. And not only that, but they also showed that his statements and his work were absolutely indispensable in the realm of physics.

AvogadroThe Avogadro’s law refers to the characteristics of the ideal gases (theoretical). Avogadro noted that the relative densities of the gases, when the same temperature and pressure conditions are registered, they are proportional to their atomic weights. From this, he formulated his hypothesis: according to Avogadro, gases with the same volume, when measured under the same temperature and pressure conditions, present the same amount of particles (atoms or molecules).

By extension, the Avogadro’s law indicates that the number of molecules of two different gases occupy an identical volume when they are under the same conditions of temperature and Pressure.

Continuing with his reasoning, Avogadro postulated that a mole (unit of measurement) of different substances contains the same number of molecules. This number has a value known as Avogadro’s number: 6.022045 x 10 to the 23rd power.

The Avogadro’s number, therefore, reveals the number of elemental entities (molecules, atoms, ions, electrons) found in one mole of any substance. Regarding the mole, we must take into account that it is equivalent to the number of atoms present in twelve grams of pure carbon-12.

Numerous are the illustrious characters who, throughout history, have not hesitated to emphasize, in a forceful way, the important role played by Avogadro as well as his constant. Specifically, among the most relevant, the following stand out:
-The French physicist Jean Perrin, winner of the Nobel Prize in 1926, who owed part of his work to the advances mentioned by the aforementioned Amedeo Avogadro.
-The Austrian chemist and physicist Johann Josef Loschmidt, who is considered one of the first students of molecular size and atomic valence.