Biography of Amedeo Avogadro, Influential Italian Scientist

Amedeo Avogadro

Mondadori Portfolio / Contributor / Getty Images

Amedeo Avogadro (August 9, 1776–July 9, 1856) was an Italian scientist known for his research on gas volume, pressure, and temperature. He formulated the gas law known as Avogadro's law, which states that all gases, at the same temperature and pressure, have the same number of molecules per volume. Today, Avogadro is considered an important early figure in atomic theory.

Fast Facts: Amedeo Avogadro

  • Known For: Formulating the experimental gas law known as Avogadro's law
  • Born: August 9, 1776 in Turin, Italy
  • Died: July 9, 1856 in Turin, Italy
  • Published Works: Essai d'une manière de déterminer les masses relatives des molécules élémentaires des corps, et les proportions selon lesquelles elles entrent dans ces combinaisons ("Essay on Determining the Relative Masses of the Elementary Molecules of Bodies and the Proportions by Which They Enter These Combinations")
  • Spouse: Felicita Mazzé
  • Children: Six

Early Life

Lorenzo Romano Amedeo Carlo Avogadro was born into a family of distinguished Italian lawyers in 1776. Following in his family's footsteps, he studied ecclesiastical law and began to practice on his own before eventually turning his attention to the natural sciences. In 1800, Avogadro began private studies in physics and mathematics. His very first experiments were conducted with his brother on the subject of electricity.


In 1809, Avogadro started teaching the natural sciences in a liceo (high school) in Vericelli. It was in Vericelli, while experimenting with gas densities, that Avogadro noticed something surprising: the combination of two volumes of hydrogen gas with one volume of oxygen gas produced two volumes of water vapor. Given the understanding of gas densities at the time, Avogadro had expected the reaction to produce only one volume of water vapor. That the experiment produced two lead him to surmise that oxygen particles consisted of two atoms (he actually used the word "molecule"). In his writings, Avogadro referred to three different types of "molecules:" integral molecules (most similar to what scientists call molecules today), constituent molecules (those that are part of an element), and elementary molecules (similar to what scientists now call atoms). His study of such elementary particles was highly influential in the field of atomic theory.

Avogadro was not alone in his study of gases and molecules. Two other scientists—English chemist John Dalton and French chemist Joseph Gay-Lussac—were also exploring these topics around the same time, and their work had a strong influence on him. Dalton is best remembered for articulating the basics of atomic theory—that all matter is composed of tiny, indivisible particles called atoms. Gay-Lussac is best remembered for his eponymous gas pressure-temperature law.

Avogadro wrote a memoria (concise note) in which he described the experimental gas law that now bears his name. He sent this memoria to De Lamétherie's Journal de Physique, de Chemie et d'Histoire naturelle, and it was published in the July 14, 1811 issue. Though his discovery is now considered a foundational aspect of chemistry, it did not receive much notice in his time. Some historians believe that Avogadro's work was overlooked because the scientist worked in relative obscurity. Although Avogadro was aware of his contemporaries' discoveries, he did not move in their social circles and he did not begin corresponding with other major scientists until late in his career. Very few of Avogadro's papers were translated into English and German during his lifetime. Additionally, his ideas were likely neglected because they contradicted those of more famous scientists.

In 1814, Avogadro published a memoria about gas densities, and in 1820 he became the first chair of mathematical physics at the University of Turin. As a member of a government commission on weights and measures, he helped introduce the metric system to the Piedmont region of Italy. The standardization of measurements made it easier for scientists in different regions to understand, compare, and evaluate each other's work. Avogadro also served as a member of the Royal Superior Council on Public Instruction.

Personal Life

Not much is known about Avogadro's private life. In 1815, he married Felicita Mazzé; the couple had six children. Some historical accounts indicate that Avogadro sponsored and aided a group of people planning a revolution on the island of Sardinia, which was ultimately stopped by the concession of Charles Albert's modern Constitution (Statuto Albertino). Because of his alleged political actions, Avogadro was removed as a professor at the University of Turin. However, doubts remain as to the nature of Avogadro's association with the Sardinians. In any case, increasing acceptance of both revolutionary ideas and Avogadro's work led to his reinstatement at the University of Turin in 1833.


In 1850, Avogadro retired from the University of Turin at the age of 74. He died on July 9, 1856.


Avogadro is best known today for his eponymous gas law, which states that equal volumes of gasses, at the same temperature and pressure, contain the same number of molecules. Avogadro's hypothesis wasn't generally accepted until 1858 (two years after Avogadro's death) when the Italian chemist Stanislao Cannizzaro was able to explain why there were some organic chemical exceptions to Avogadro's hypothesis. Cannizzaro helped clarify some of Avogadro's ideas, including his view of the relationship between atoms and molecules. He also provided empirical evidence by calculating the molecular (atomic) weights of various substances.

One of the most important contributions of Avogadro's work was his resolution of the confusion surrounding atoms and molecules (although he didn't use the term "atom"). Avogadro believed that particles could be composed of molecules and that molecules could be composed of still simpler units (which we now call "atoms"). The number of molecules in a mole (one gram molecular weight) was termed Avogadro's number (sometimes called Avogadro's constant) in honor of Avogadro's theories. Avogadro's number has been experimentally determined to be 6.023x1023 molecules per gram-mole.


  • Datta, N. C. "The Story of Chemistry." Universities Press, 2005.
  • Morselli, Mario. "Amedeo Avogadro: a Scientific Biography." Reidel, 1984.
mla apa chicago
Your Citation
Helmenstine, Anne Marie, Ph.D. "Biography of Amedeo Avogadro, Influential Italian Scientist." ThoughtCo, Jun. 28, 2021, Helmenstine, Anne Marie, Ph.D. (2021, June 28). Biography of Amedeo Avogadro, Influential Italian Scientist. Retrieved from Helmenstine, Anne Marie, Ph.D. "Biography of Amedeo Avogadro, Influential Italian Scientist." ThoughtCo. (accessed February 4, 2023).