Atomic theory

Developing Atomic Theory

  • 400

    Democritus 400BC

    Democritus 400BC
    Democritus called a particle that could not be broken down any further an "atomos", meaning invisible. His ideas were dismissed for those of Aristotle.
  • 401

    Aristotle 350BC

    Aristotle 350BC
    In 350BC Aristotle stated that everything was made from the four basic foundations : earth, wind, fire and water.
    His ideas were the more favourable of the time, even though the ideas of Democritus were more accurate.
  • Robert Boyle

    Robert Boyle
    Boyle experimented with the behaviour of gases, particularly when they were placed under pressure. He developed a law describing this behaviour, that was named after him (Boyle's Law).
    His experiments and observations suggested a similar model to that which Democritus had suggested many years earlier.
  • John Dalton's "Billiard Ball Model"

    John Dalton's "Billiard Ball Model"
    Called the "billiard ball model" as Dalton thought atoms were solid spheres.
    Dalton Explained compounds and particles as:
    - All matter is made up of small particles called atoms
    - Atoms cannot be created nor destroyed, nor divided into smaller particles
    - All atoms of the sme element are identical, and are different in size and mass from atoms of other elements
    - Compounds are created when atoms of different elements link together in fixed proportions
  • JJ Thomson "Raisin-bun model"

    JJ Thomson "Raisin-bun model"
    First person to discover a subatomic particle.
    Through cathode ray experiments Thomson developed his "rasin-bun" model, that descrived the atom as a positively charged sphere in which negatively charged electrons were embedded.
  • Ernest Rutherford, "Planetary Model"

    Ernest Rutherford, "Planetary Model"
    1898 - 1907
    Rutherford proposed that the atom was made up of a very small positively-charged nuclues, surrounded by orbitting elections. He also stated that most of the mass was in the nulcues of the atom and the rest of the atom was mostly empty space.
  • Niels Bohr, "Bohr Model"

    Niels Bohr, "Bohr Model"
    Bohr studied with Rutherford and found that the "planetary" model did not adequately explain some of the behaviour of certain elements, so he modified this model to suggest that electrons rotated around the nucleus in specific energy levels or fixed pathways (orbits).
  • Present Day - "Electron Cloud Model"

    Present Day - "Electron Cloud Model"
    The quantum mechanics model describes electrons as existing in a charged could around the nucleus. There are areas of greater likelihood of finding an electron, indicated by the orbitals.