DALTON ATOMIC MODEL: POSTULATES - PHYSICAL - 2025

The atomic model of Dalton and Dalton 's atomic theory was a proposal submitted between 1803 and 1807 by chemist John Dalton math and English. This was the first proposal for a conceptual organization regarding the structure and functioning of atoms.

Dalton's model is also known as a spherical model, since it proposes the fact that the atom is an indivisible, solid and compact sphere. This model made it much easier to explain chemistry to the rest of the world and it was the basis for the many innovative research projects that followed. It was possible to explain why the substances reacted in certain states.

Copy of the first page of John Dalton's book A New System of Chemical Philosophy (1808)

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

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

Dalton Atomic Model Postulates

John dalton

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

Postulate 1

The image above shows a summary of Dalton's model: the atoms would be indivisible, indestructible and homogeneous tiny spheres.

Dalton's first postulate established that elements are made up of tiny particles called atoms, which cannot be divided nor can they be destroyed.

Also, Dalton commented that said particles could not change in any chemical reaction either.

Postulate 2

Color blind symbols. (1911 Britannica)

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

On the other hand, it also established that the atoms of different elements have different masses. From this proposal arose the knowledge of the relative atomic weights that were demonstrated when comparing different elements with hydrogen.

Postulate 3

Atoms of hydrogen, nitrogen and carbonic acid (A new system of chemical philosophy, 1808)

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

The combination of atoms, both 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 and complete numbers. This expression will not be displayed in fractions, since the atoms are indivisible.

Postulate 5

Dalton's fifth postulate established that there is the possible combination of different atoms in different proportions to form more than one compound.

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

Postulate 6

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

Dalton Atomic Model Errors

Like all theory in the world of science, there were many refutations regarding the model proposed by Dalton, which were demonstrated over the years leaving behind Dalton's innovative ideas.

Water formula

An example of this was the argument given by Dalton on the formula of water, which according to him was composed of a hydrogen and an oxygen.

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

A few years later, the European scientists Gay-Lussac and Alexander von Humbodt refuted this information and showed that water was actually composed of two hydrogens and one oxygen. 6 years later Amadeo Avogadro specified the exact composition of the water and because of it there is Avogadro's Law.

Composition of atoms

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

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

Conclusions

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 today.

Dalton's atomic model was not questioned for decades due to its relevance in the world of science and its accurate explanation of the investigations and hypotheses that were presented at that time in the history of science.

Dalton's main contributions

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

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

Forerunner of atomic theories

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

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 foundations of what we know today as modern chemistry.

First to publish a table of chemical weights

Dalton was the first scientist to have 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 to mold what would be his atomic model.

Naming Color Blindness

It should be noted that Dalton was one of the first recorded people with visual problems to capture colors and because of him this condition is named as color blindness.

Articles of interest

Schrödinger's atomic model.

De Broglie atomic model.

Chadwick's atomic model.

Heisenberg atomic model.

Perrin's atomic model.

Thomson's atomic model.

Dirac Jordan atomic model.

Atomic model of Democritus.

Bohr's atomic model.

Rutherford's atomic model.

References

1. Dalton's atomic theory. Retrieved on November 24, 2017, from Khanacademy: www.khanacademy.org
2. Dalton's Atomic Theory. Retrieved on November 24, 2017, from Indiana University Northwest: iun.edu
3. Atomic theory. Retrieved on November 24, 2017, from Encyclopædia Britannica: www.britannica.com
4. Atomic Theory. Retrieved on November 24, 2017, from Wikipedia: en.wikipedia.org
5. History of Atomic Structure. Retrieved on November 24, 2017, from Lumen: courses.lumenlearning.com.