History of the atom

By D-AX
  • 442 BCE

    Democritus

    The concept of the atom as a basic and indivisible block that composes the matter of the universe was postulated by the atomist school in Ancient Greece, in the fifth century BC. C., being Democritus one of its exponents.
  • Period: 400 BCE to

    Aristotle

    Postulates that matter was formed by these 4 elements but denies the idea of ​​atom, a fact that was maintained until 2000 years later in the thought of humanity. After the Scientific Revolution, the Greek atomist school was reconsidered by the new generations of scientists of the mid-19th century, when their concepts were introduced to explain the chemical laws. With the development of nuclear physics in the 20th century it was found that the atom can be subdivided into smaller particles.

  • John Dalton

    Matter is made up of particles called atoms, which can not be destroyed.
    Atoms of same element are equal to each other, they have own weight and own qualities. The atoms of different elements have different weights.
    Atoms remain indivisible, even when combined in chemical reactions.
    Atoms, when combined to form compounds, keep simple relationships.
    Different elements can be combined in different proportions and form more compound.
    Chemical compounds are formed joining atoms of 2 or more atoms.

  • Thomson

    Thomson devised an atom similar to a fruit cake. A positive cloud that contained the negative particles (electrons) suspended in it. The number of negative charges was adequate to neutralize the positive charge. In the case that the atom lost an electron, the structure would remain positive; and if he won, the final charge would be negative.Later Jean Perrin proposed a modified model from Thomson where "raisins" (electrons) were located on the outside of the "cake" (protons).

  • Rutherford

    It represents an advance on the Thomson model
    It maintains that the atom is composed of a positive and a negative part. However, it postulates that the positive part is concentrated in a nucleus, which also contains all the mass of the atom, while the electrons are located orbiting the nucleus in elliptical orbits with a space empty between them. Being an obsolete model, it is the most common perception of the atom.
    However, the atomic model of Rutherford presented several inconsistencies

  • Niels Bohr

    Is a model of the Rutherford model.
    Electrons can be only in certain orbits
    Each orbit has an associated energy. The outermost is the most energy.
    Electrons do not radiate energy (light) while they remain in stable orbits.
    Electrons can jump from one orbit to another. If you do it from a lower energy to a major energy absorbs a quantity of energy equals to the energy difference associated with each orbit. If you go from a higher to a lower, you lose energy in the form of radiation (light).