1913 bohr2

History of the Atomic Theory

By buddytheelf
  • 400

    Democritus

    Democritus
    (460-370 BC)
    Democritus was a Greek philosopher. He believed that everything was made up of atoms. Atoms are always in motion, indestructable, there are an infinite number of atoms and kinds of atoms, and they are different shapes and sizes.
    *sited from worksheet

  • John Dalton

    John Dalton
    atomic theory
    (1766-1844)
    Dalton believed that all matter is made of atoms and that atoms are indestructible and indivisible. Atoms can not be created or destroyed. Dalton believed a chemical reaction was the rearrangement of atoms. Compounds are made up of a combination of two or more different kinds of atoms. Lastly, he believed that all atoms in an element are identical in mass and properties.

  • J.J. Thomson

    J.J. Thomson
    this link and worksheet
    (1856-1940)
    Thomson was the first to discover that atoms had smaller subatomic particles. He discovered negative particles called electrons. J.J. made a model that looked like a chocolate chip cookie, also called the plum pudding theory. The electrons were the chocolate chips and the rest of the cookie was the positive charge.

  • Ernest Rutherford

    Ernest Rutherford
    atomic theory
    (1871-1937)
    Rutherford discovered that the positive charge in an atom was concentrated in the center. He also found that most of the atom was empty space. He came up with this theory by using the gold foil experiment.

  • Niels Bohr

    Niels Bohr
    atomic theory
    (1885-1962)
    Bohr revised Rutherford's model. He suggested that electrons: orbit the nucleus without loosing energy, can only move in fixed orbits of specific energies, and that electrons that had low energy would orbit closer to the nucleus while high energy electrons would orbit further from the nucleus.

  • Paul Dirac

    Paul Dirac
    atomic theory
    (1902-1984)
    Dirac observed that every particle has an anti-particle and when they come in contact with each other, they form a burst of energy. He discovered this while formulating an equation for electrons.

  • James Chadwick

    James Chadwick
    atomic theory
    (1891-1974)
    Chadwick came up with the neutron. His discovery proved Rutherford's prediction. A neutron is a particle with a nuetral charge.