History of the Atom

By mcinslay
  • 460 BCE

    Democritus

    Democritus
    Democrutis developed the idea of the atom. His atomic theory stated that all matter consists of invisible particles called atoms, atoms are indestructible, atoms are solid but invisible, atoms are homogenous, atoms differ in size, shape, mass, position, and arrangement.

  • Dalton

    Dalton
    His atomic theory said that elements consisted of tiny particles called atoms. It states an element is one of a kind because all atoms of an element are identical. All the atoms that make up the element have the same mass. All elements are different from each other due to differing masses. A compound is a pure substance due to different elements bonded together. They are not easily separated from one another. Compounds have a fixed ratio of atoms. Each atom has its own characteristics.

  • J. J. Thomson

    J. J. Thomson
    J.J. Thomson discovered electrons and noticed that an atom can be divided. Also, he concluded atoms are made of positive cores and negatively charged particles within it. He developed the Plum Pudding Model before the atomic nucleus was discovered.

  • Ernest Rutherford

    Ernest Rutherford
    Rutherford's most famous experiment is the gold foil experiment. It consisted of shooting Alpha atoms into extremely thin gold foil and seeing where on the surrounding circular wall it hit. He believed they would all just go straight through. However, a very small amount went either off to the sides or back towards the Alpha atom stream. This he found meant that there was something in the center of the atoms, called the nucleus. This led to his nuclear model of an atom.

  • Niels Bohr

    Niels Bohr
    In 1913, he passed on to a study of the structure of atoms on the basis of Rutherford's discovery of the atomic nucleus, and since 1920 he was at the head of the Institute for Theoretical Physics, established for him at that university.

  • Niels Bohr part 2

    Niels Bohr part 2
    This model of Bohr’s idea of the atomic structure shows how it works. The nucleus lies in the center of the model and is made up of a certain number of protons and neutrons. Each of the outer layers is made up of a certain amount of electrons. The limit to how many electrons can be in each electron shell is shown in the model. This model helps not only with the theoretical appearance of an atom, but also how different elements combine.