Dalton’s Atomic Model Theory Postulates Features

Dalton’s atomic model: It is important to understand that much of what we know regarding the structure ofDalton's atomic model atoms has been developed over a long period of time. This is the way that scientific knowledge is generally developed, with one person drawing on someone else’s ideas. The idea of ​​atoms was invented by two Greek philosophers, Democritus and Leucippus in the 5th century BC. The Greek word ατoμoν “atom” means indivisible and this name was given because the two scientists believed that atoms could not be divided into smaller pieces.

What is Dalton’s atomic model?

The atomic model of Dalton is the first atomic model tells us that all matter is composed of very small things that can not be destroyed and which are called atoms .

  • What is Dalton’s atomic model?
  • features
  • Dalton’s atomic model postulates
  • Model errors
  • Contributions
  • Experiment
  • What problems does Dalton’s atomic model present?
  • Importance

This model consisted of the first conceptualization of the functioningstructure, and arrangement of atoms. The English scientist John Dalton called it at the time as “atomic theory ” or “atomic postulates”. The model was postulated in 1803, and is considered the first atomic model , and the following is postulated:

  • That matter is made up of indivisible, indestructible, and extremely small particles known as atoms.
  • That the atoms that are within the same element are identical to each other so they have the same mass and properties.
  • That the atoms found in different elements also have different mass and different properties.
  • The compounds are formed by the union of atoms which are in constant and simple proportions.


Among the most representative characteristics of atoms we can mention the following:

  • It is also known as a spherical model since it says that the atom is an indivisible, solid, and compact sphere.
  • It is considered the basic unit of all matter.
  • The theory had six different postulates.
  • The atoms of two elements interact with each other to form molecules.
  • He stated that matter was made up of tiny particles called atoms.
  • The atoms of the same elements are equal to each other.
  • The atoms of a different element also have different weights.

Dalton’s atomic model postulates

Dalton’s atomic model theory had six different postulates which were:

  • First postulate: specified that the atoms were indivisible, indestructible, and homogeneous tiny spheres. It also established that the elements were formed by atoms and that these particles could not change before any type of chemical reaction.
  • Second postulate: it established that the atoms that were in the same element were equal both in weight and in other characteristics, it said that the atoms of these elements had different mass giving rise to the atomic weights.
  • Third postulate: this postulate established that atoms cannot be divided even when in the presence of chemical reactions, nor could they be created or destroyed. The combination of atoms gives rise to complex compounds but the atom will continue to be the minimum unit of matter.
  • Fourth postulate: it established that although combinations were made to form compounds, they would have a relationship that could be explained by means of simple and complete numbers.
  • Fifth postulate: it said that there was the possibility of combining different atoms in also different proportions that could give rise to more than one compound and thus an explanation was found about the number of atoms that existed in the universe.
  • Sixth postulate: it established that all chemical compounds had been formed by the combination of the atoms of two or more different elements.

Model errors

Like many theories, a number of refutations have been put forward regarding the model that was proposed by Dalton. An example was the formula for water given by Dalton, which was made up of hydrogen and oxygen, based on this statement there were many miscalculations in the mass and weight of the compounds that made up the water.

Later, in the 20th century, the true composition of atoms showed that there was a unit smaller than the atom, which was the protons, neutrons, and electrons.

Contributions of Dalton’s atomic model

The contributions to the world of Dalton’s atomic model were the following:

  • With him the first attempt was made to understand the basic constitution of matter .
  • It confirmed the theoretical laws that had been raised previously.
  • The chemical scale of atomic masses was created.
  • Chemistry began to be seen as an exact and mathematical science .
  • He taught us that matter was made up of indivisible atoms and that when atoms combined they gave rise to compounds.


Dalton carried out three experiments with cathode ray tubes, and during his third experiment, he drew a series of conclusions and decided to call ” corpuscles ” the particles that came from inside the atoms of the electrodes, forming the cathode rays.

The cathode tube was a closed empty glass tube, to which the air was removed and gas was introduced at reduced pressure. After conducting his experiment, he concluded that atoms are divisible.

What problems does Dalton’s atomic model present?

The error that Dalton had in his theory was to affirm that matter was not composed or formed by smaller particles that were not atoms , but despite this inconvenience, his contribution established the foundations of modern Physics and Chemistry which gave way to true atomic discoveries.

Importance of Dalton’s atomic model

The importance of Dalton’s atomic model lies in that it allowed us to clarify why chemical substances could react in fixed stoichiometric proportions, which we now know as the Law of constant proportions, and it allowed us to know why when two substances react to form two or more unequal compounds, the proportions of these relations are integers, assuming that we know by the name of the Law of multiple proportions. Furthermore, he taught us that the basic unit of matter is the atom.

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