Amedeo Avogadro
Italian scientist who proposed Avogadro's law on gases.
Amedeo Avogadro was an Italian scientist born in Turin to a noble family of the Kingdom of Sardinia. He initially studied ecclesiastical law, graduating at age twenty and practicing for a time, before turning his focus to physics and mathematics. In 1809, he began teaching these subjects at a high school in Vercelli. His most famous contribution, Avogadro’s law, emerged from an 1811 essay submitted to a journal of physics, chemistry, and natural history. The law states that equal volumes of any gases, under identical temperature and pressure, contain the same number of molecules. This hypothesis was developed in response to Joseph Louis Gay-Lussac’s earlier work on combining gas volumes. A key difficulty Avogadro addressed was the prevailing confusion between atoms and molecules; he distinguished them by proposing that gases consist of molecules, which themselves are composed of atoms, though he used the term “elementary molecule” for what is now called an atom. He also emphasized the concept of mass as distinct from weight. Avogadro later became a professor of physics at the University of Turin in 1820, but lost his position in 1823 due to his involvement in a revolutionary movement. He was recalled to the university in 1833 and taught for another twenty years. His private life was sober and religious; he married Felicita Mazzé and had six children. Beyond his scientific work, he held posts in statistics, meteorology, and weights and measures, introducing the metric system into Piedmont, and served on a council on public instruction. In his honor, the number of elementary entities per mole of a substance is called the Avogadro constant, a fundamental constant of the SI system.
- field
- Physics, chemistry, mathematics
- nationality
- Italian (Kingdom of Sardinia)
- known_for
- Avogadro's law, Avogadro constant
Lore & Background
Amedeo Avogadro was born in Turin to a noble family of the Kingdom of Sardinia. He graduated in ecclesiastical law at age 20 and began practicing, but soon turned to physics and mathematics. He began teaching these subjects at a liceo in Vercelli in 1809. In 1811, he published an essay containing what became known as Avogadro's law, which states that equal volumes of gases under the same temperature and pressure contain equal numbers of molecules. This work distinguished between molecules and atoms, clarifying that gases are composed of molecules made of atoms, and addressed the confusion between the terms "atom" and "molecule" at the time. He became a professor of physics at the University of Turin in 1820 but lost his position in 1823 due to his involvement in a revolutionary movement. He was recalled to the university in 1833 and taught for another twenty years. Avogadro also held posts in statistics, meteorology, and weights and measures, introducing the metric system into Piedmont. He married Felicita Mazzé and had six children. His private life was sober and religious. He died on 9 July 1856. In his honor, the number of elementary entities per mole of a substance is named the Avogadro constant, one of the seven defining constants of the SI system.
Reader's Guide
Avogadro's law established that equal volumes of any gas, under identical temperature and pressure, contain the same number of molecules. This principle allowed chemists to calculate the relative molecular masses of gases by comparing the masses of equal volumes. A key advance was Avogadro’s clear separation of the concepts of atoms and molecules—he proposed that gases consist of molecules, which themselves are made of atoms, a distinction that resolved significant confusion in early chemistry, as figures like John Dalton had not considered it. Despite its importance, the scientific community initially paid little attention to his theory, and it was not immediately accepted; André-Marie Ampère proposed a similar idea a few years later. The Avogadro constant, the number of elementary entities per mole of a substance, is named in his honor and is one of the seven defining constants of the SI system, used to precisely compute the outcomes of chemical reactions. Beyond his molecular work, Avogadro held official posts in statistics, meteorology, and weights and measures, and he introduced the metric system into Piedmont. His personal life was sober and religious; he married Felicita Mazzé, had six children, and served on the Royal Superior Council on Public Instruction.
Did You Know?
- Avogadro graduated in ecclesiastical law at age 20 before turning to physics and mathematics.
- Avogadro introduced the metric system into Piedmont.
Frequently Asked Questions
Who is Amedeo Avogadro?
Amedeo Avogadro was an Italian nobleman and scientist from the Kingdom of Sardinia who made foundational contributions to physics, chemistry, and mathematics. He is most widely recognized for formulating what we now call Avogadro's law regarding the behavior of gases.
What is Avogadro's law?
Avogadro's law states that when two or more gases are held at the same temperature and pressure, equal volumes of those gases contain the same number of molecules. This principle was a key step in establishing modern molecular theory.
What is the Avogadro constant?
The Avogadro constant is the number of elementary particles—atoms, molecules, or other units—found in one mole of a substance. It was named in honor of Amedeo Avogadro to recognize his foundational work on molecular theory.
When was Amedeo Avogadro born and when did he die?
Avogadro was born on 9 August 1776 and passed away on 9 July 1856. He lived his entire life in the Kingdom of Sardinia, which is part of modern-day Italy.
Why is Amedeo Avogadro important in the history of science?
Avogadro's insight that equal gas volumes contain equal molecule counts resolved long-standing confusion about atomic and molecular weights, laying groundwork for modern chemistry. His legacy endures in both the law and the constant that bear his name.
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