Introduction
Atom, the building unit of everything, has been a matter of controversy for decades. The atomic theory kept evolving over time in order to explain the nature of atoms and matter.
Discovery of the atomic theory
Starting from being a philosophical topic at 500 B.C till the evolution of quantum mechanics, the atomic theory was first put by Democritus who illustrated that the matter contains indivisible units called “atoms”. Later in 1789 Antoine Lavoisier concluded that the masses of products in a reaction equals the mass of reactants, known as the “law of mass conservation”.
It wasn’t until 1808 that the atomic theory was finally illustrated when John Dalton published his paper “on chemical synthesis” (Dalton 1808) in which he proposed that every element has only one type of atom that can never be destroyed by chemical methods.
In 1897 J.J Thomson described the plum pudding model stating that electrons are embedded in a mass of positive charge giving an electrically neutral atom, this theory was later disproved by Rutherford in 1909 who stated a planetary model where electrons revolve around a positive nucleus.
Four years later, Niels Bohr proposed the "Bohr model" demonstrating that electrons orbit the nucleus at certain distances and that electrons can make quantum leaps between different energy levels. That was a remarkable new era in quantum mechanics which led to an improved atomic theory where atoms have smaller structures inside them.
in 1913 Frederick Soddy introduced the concept of “isotopes” defined as several forms of an atom with a different number of neutrons. In the current time, scientists are interested in the smaller particles inside the neutrons, protons and electrons.
Up till this moment, scientists are still looking for more sophisticated theories that can describe everything about the atom, since every existing matter started from a small atom, this quest will never end.
Works Cited
- Helmenstine, Anne Marie, PhD. "A Brief History of Atomic Theory." ThoughtCo, Dec. 3, 2018, thoughtco.com/history-of-atomic-theory-4129185.
- Dalton, John. "On chemical synthesis." Foundations of the Atomic Theory (1808): 29.
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