Modern Physics

Dalton’s Atomic Model: Postulates

The atomic model of Dalton and Dalton’s atomic theory was a proposal put forward between 1803 and 1807 by the English chemist and mathematician John Dalton. This was the first proposal for a conceptual organization in relation to the structure and functioning of atoms.

Dalton’s model is also known as the spherical model, as it proposes the fact that the atom is an indivisible, solid and compact sphere. Thanks to this model, it was much easier to provide an explanation of chemistry to the rest of the world and it was the basis of the many innovative research projects that followed. It can be explained why substances react in certain states.

According to Dalton, matter was composed of a minimal unit called atom, which could not be destroyed or divided in any way. This unit, previously proposed by Democritus and his mentor Leucipo, was the basis for Dalton’s research and the creation of his atomic model .

With this atomic theory, John Dalton tried to retake the ideas of the Greek philosophers about the existence of the atom (atomic theory of the universe), but using as a platform several laboratory experiments that allowed him to demonstrate his ideas.

Postulates of Dalton’s Atomic Model

Dalton formulated his atomic model with 6 postulates, where he explains on what he based his studies and how he carried them out.

Postulate 1

Dalton’s first postulate established that elements are made up of small particles called atoms, which cannot be split or destroyed.

Likewise, Dalton commented that these particles could not change in any chemical reaction either.

Postulate 2

Colorblind symbols. (British 1911)

Dalton’s second postulate established that all atoms present in the same element are equal in weight and other characteristics.

On the other hand, it also established that atoms of different elements have different mass. This proposal resulted in the knowledge of the relative atomic weights that were demonstrated when comparing different elements with hydrogen.

Postulate 3

Dalton’s third postulate stated that atoms are indivisible even when combined in chemical reactions. Neither can they be created or destroyed.

Combining atoms, the same and different, will generate more complex compounds, but this process will not change the fact that the atom is the smallest unit of matter.

Postulate 4

Union of atoms combined in proportions. John Dalton (1808).

Dalton’s fourth postulate stated that even when atoms are combined to form a compound, they will always have a relationship that can be expressed in simple, complete numbers. This expression will not be shown in fractions as atoms are indivisible.

Postulate 5

Dalton’s fifth postulate stated that there is a possible combination of different atoms in different proportions to form more than one compound.

In this way, it could be explained that from a finite amount of atoms all the matter existing in the universe came.

Postulate 6

Dalton’s sixth and final postulate stated that each and every chemical compound was created from the combination of atoms of two or more different elements.

Dalton atomic model errors

Like any theory in the world of science, there have been many rebuttals to Dalton’s proposed model that have been demonstrated over the years, leaving Dalton’s innovative ideas behind.

water formula

One example of this was Dalton’s argument about the formula for water, which he said was made up of hydrogen and oxygen.

Due to this statement, there were many miscalculations regarding the mass and weight of some basic compounds that were based on this information.

A few years later, European scientists Gay-Lussac and Alexander von Humbodt refuted this information and demonstrated that water was actually composed of two hydrogens and an oxygen. 6 years later, Amadeo Avogadro pointed out the exact composition of water and, therefore, there is the Avogadro Law.

composition of atoms

On the other hand, in the 20th century, the true composition of atoms was revealed. In this case, it has been shown that there is a smaller unit such as protons, electrons and neutrons.

Likewise, the various atomic weights established in the periodic table of Mendeyev and Meyer, the existence of isotopes and the more specific chemical properties emerged.


Despite his mistakes, John Dalton’s contributions were of great relevance in the world of science and caused a stir in his time due to the large amount of information he provided.

His scientific contributions are still valid and are still being studied.

Dalton’s atomic model has not been questioned for decades due to its relevance in the world of science and its correct explanation for the research and hypotheses that were put forward at that time in the history of science.

Dalton’s main contributions

His contribution to the world of science was primarily to clarify and formulate hypotheses about nature through quantitative essays.

The scientist died of a heart attack on 27 July 1884 in Manchester and shortly thereafter received honors from the monarchy.

Precursor of Atomic Theories

John Dalton was an English chemist, mathematician and naturalist. He was born on September 6, 1766 in Cumberland, United Kingdom, and has been known as one of the forerunners of atomic theories since the moment he presented his Atomic Model.

He laid the foundations of modern chemistry

Dalton is known as one of the forerunners in creating a table of relative weights for chemical elements. This fact helped lay the groundwork for what we now know as modern chemistry.

First to publish a chemical weight table

Dalton was the first scientist who had the honor of publishing a table of atomic weights that included elements such as hydrogen, oxygen, phosphorus, carbon and sulfur. Thanks to this publication, Dalton began to work and shape what would be his atomic model.

name color blindness

Note that Dalton was one of the first recorded people with visual problems to capture color, and because of this, this condition is called color blindness.

articles of interest

Schrödinger Atomic Model.

Broglie’s atomic model.

Chadwick Atomic Model.

Heisenberg Atomic Model.

Perrin atomic model.

Thomson Atomic Model.

Atomic model of Dirac Jordan.

Atomic model of Democritus.

Bohr atomic model.

Rutherford Atomic Model.

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