History of atomic theory

History Of Atomic Theory

Atomic theory is one of the most important theories developed in time in the field of physics and chemistry. The theory analyzes the nature of matter, stating that matter is composed of small units called atoms. Atomic theory formed since antiquity and was constantly improved since by the works of scientists.

Initially the theory of matter formed of atoms was approached in a more philosophical way, the scientific part of the theory being developed later in the 19th century. Greek antiques were the first to claim that matter was composed of indivisible units, but their approach was not based on experiment as it was rather a philosophical attempt to explain the universe. The Greek word atomos means indivisible and the theory of atoms was clearly defining that matter was composed of units obtained once you divide matter until no further division is possible, as presented by the Greek philosophers Leucippus and Democritus (History of atomic theory). Some understandings of Aristotle claim that the great philosopher himself allowed the idea that there is a minima in natural things. (Ancient Atomism)

Atomic theory was further analyzed and developed beginning with the 19th century, when John Dalton analyzed more closely the theory of atoms and presented the first results about the nature of atoms. He made a great contribution to the theory as he argued that atoms of one element are identical among each other, but that they are not identical with atoms of a different element. He also argued that combined atoms of different elements can create more complex substances, called chemical compounds (History of atomic theory). Comparing to the Greek theory, Dalton's was focused on the properties of substance and not its form. Dalton's conclusions proved to be correct and although his theory was further developed, he set the basis for modern atomic theory.

Dalton's research was based on the works of several other scientists and chemists, such as Antoine Lavoisier's 1789 law of conservation of mass or law of definite proportions first proven by Joseph Louis Proust in 1799 (Atomic Theory).

However, Dalton's theory of atoms was not complete or entirely correct and his work was further improved by the works of Amadeo Avogadro and others. In 1897, J.J. Thompson revealed that the atom was not the smallest particle as he discovered the electron, proving that there are other particles called elementary particles. Thomposon was also the first to discover the existence of isotopes.

Atomic theory was further improved by the works of Ernest Rutherford, who "discovered that most of the mass and positive charge of an atom is concentrated in a very small fraction of its volume, which he assumed to be at the very center" (Atomic Theory), the center being called nucleos.