The 9 postulates of Dalton’s atomic theory

Today we all know that matter is made up of small particles called molecules which in turn are made up of atoms of different elements (which are now known to be made up of different subatomic particles such as protons, neutrons and electrons).

But while the precursors already existed even in ancient Greece, it was not until 1803 that the theory developed at the scientific level that matter is made up of basic and indivisible units that come together to form different compounds, considering the atoms these indivisible units and compound atoms, or what Avogadro would later call molecules, the compounds formed through them.

It’s the Dalton’s atomic theory, Who developed different postulates or principles that attempted to give an explanation to the configuration of matter.

    John Dalton: Brief Introduction to the Creator of Atomic Theory

    The figure of John Dalton is widely known to be the founder of atomic theory and also to investigate and publicize the visual impairment known as color blindness, from which he also suffered. This scientist was born in Great Britain in 1766, the son of a working family with few resources. Despite the difficulties, Dalton would learn science and math in school and even continue to teach at the age of twelve. Eventually, he will open and run a school, alongside his brothers.

    later is he broadened his interest in various sciences such as astronomy and geography, Coming to lecture on the issue. He was considering studying medicine, but would be disheartened by his surroundings. He has conducted various research and publications in various fields, including meteorology and even grammar. One of the best known today is the lack of color perception from which he himself suffered and is now known as color blindness.

    He would also study other phenomena such as heat, the behavior of gases and different elements. His work in these latter fields will lead him to reflect on the composition of matter, which will eventually lead to the development of atomic theory.

      Dalton’s atomic theory

      One of Dalton’s most important and recognized contributions to the field of science is his conception of atomic theory. This theory established a model that sought to explain the behavior of matter as well as the fact that the combination of different proportions of different substances can generate different compounds, explaining the composition of complex elements from different balances of other substances.

      The various investigations that Dalton would lead would lead him to think that everything counts it is composed of compounds and elements, Being the first formed by combinations of the second. There are a number of indivisible particles, called atoms, which form the basis of different particles and have different characteristics from each other. Each of the elements is made up of atoms of different classes. Dalton’s theory recovers concepts typical of ancient philosophers, such as the concept of the atom from the Greek Democritus, but with a slightly different meaning from the original.

      Thus, Dalton did not believe that all matter could be identified with a single substance, but rather atoms of different types and characteristics existed, with weight being one of the most studied variables. In fact, the creator of the atomic theory came to draw up an array of elements based on the weight assigned to each of the known types of atoms, such as hydrogen and oxygen (although this initial array was not correct due to ignorance and the difficulty of measuring the weight of the different particles with the techniques of the time). It is also thanks to him that hydrogen is considered the basic model in terms of considering the atomic mass of each element, being the lightest element.

      Dalton’s postulates

      Dalton’s atomic theory it can be summarized on the basis of a number of postulates, Which are described below.

      1. the question it is entirely composed of atoms, Indivisible units of matter which cannot be generated or destroyed.
      2. Atoms of a particular element they have in all cases the same size, the same weight and the same qualities, Being all equal to each other.
      3. The characteristics of atoms of different elements they are also always different, Having different characteristics.
      4. Although they can combine with other substances to form different compounds, the atoms themselves remain unchanged, Cannot be divided or destroyed.
      5. Compounds are formed by the combination of atoms of at least two different elements.
      6. The combination of different types of atoms it is achieved through simple relationships.
      7. The combination of two specific elements can lead to different compounds according to the proportions in which they are mixed.
      8. In chemical reactions it is possible to create, dissociate or transform molecules, Being these a reorganization of the atoms that make up each compound.
      9. The same compound is always produced in the same proportion in the combination of atoms.

      Some aspects that the most recent evidence has contradicted

      Dalton’s atomic theory was one of the most important in science to describe the structure of matter. However, from the time this theory was developed a lot of progress has been made which have shown that some of the postulates defended by the author are not true.

      For example, the fact that the atom is a basic and indivisible unit turned out to be false, being able to distinguish within the atom different parts formed by subatomic structures such as protons, neutrons, and electrons.

      It is also uncertain whether all atoms of the same substance have equal properties. We can find atoms of different electric charges depending on the balance between protons and electrons (what we call ions), as well as different atomic masses of the same element (isotopes).

      A third aspect that turned out to be different from Dalton’s atomic theory is the fact that atoms are immutable, which it was denied with the advent of nuclear fusion and fission.

      While the evidence has shown that some of the postulates are not entirely true, Dalton’s theory laid the groundwork for modern chemistry and made great strides in the understanding of matter and its behavior.

      Bibliographical references:

      • Gribbin, J. (2006). History of science: 1543-2001 (2nd edition). Barcelona: Crítica, SL
      • Petrucci, R .; Harwood, W .; Herring, G. and Madura, J. (2007). General chemistry. 9th ed. Upper Saddle River, New Jersey: Pearson Prentice Hall.
      • Rosental, M. and Iudin, P. (1973). Philosophical dictionary. Editions of the universe.
      • Solitude, I. (2010). Chemistry and atomic theory. General chemistry. UNED, 22-23.

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