Evolution of Atomic Model

By lauferw
  • 300

    Democritus

    Democritus
    400 B.C.E. What: He created the first atomic model. How: His model of the atom depended on analogies from human senses.
  • 350

    Aristotle

    Aristotle
    400 B.C.E. What: He developed a theory that was based on the four elements. How: Aristotle’s theory made a great generalization of all matter of the four elements: fire, water, earth, and air. He also believed that there were four qualities to these elements: dryness, hotness, coldness, and moistness.

  • John Dalton

    John Dalton
    What: Proposed his modern theory of the atom. How: He based it upon : 1. Matter is made up of atoms that are indivisible and indestructible. 2. All atoms of an element are identical. 3. Atoms of different elements have different weights and different chemical properties. 4. Atoms of different elements combine in simple whole numbers to form compounds. 5. Atoms cannot be created or destroyed. When a compound decomposes, the atoms are recovered unchanged.

  • J.J. Thompson

    J.J. Thompson
    What: He discovered the Plum Pudding Model of the atom. How: In J.J.'s model, the atom is composed of electrons surrounded by an area of positive charges to balance out the negative charges.

  • Ernest Rutherford

    Ernest Rutherford
    What: Theorized that atoms have their positive charge concentrated in a very small nucleus. How: He pioneered the Rutherford model of the atom, with his discovery and interpretation of Rutherford scattering in his gold foil experiment.

  • Niels Bohr

    Niels Bohr
    What: Presented a picture of an atomic structure. How: He passed on to a study of the structure of atoms based on Rutherford's discovery of the atomic nucleus. (This lead him to the picture of his atom.)

  • Erwin Schrödinger

    Erwin Schrödinger
    What: He generated a mathematical model for the distribution of electrons in an atom. How: The solution to the Schrodinger Equation lead to Quantum numbers which provide the address of the electrons in an atom.

  • Werner Heisenberg

    Werner Heisenberg
    Overview of the atomic theoryWhat: The foundations of Quantum Mechanics and the "cloud model" of the atom. THe Uncertainty Principle stated simplistically that the more precisely the position of an electron is determined, the less precisely the momentum (mass & velocity) is known in this instant, and vice versa.

  • James Chadwick

    James Chadwick
    What: He proved the existence of neutrons. How: He heard of a new method of detecting particles emitted by radioactive elements developed by Irene Joliot-Curie.