Historical Development Of Atomic Theory

Timeline created by mitchell.d.andrews
  • Aug 6, 1000

    Democritis

    460BC-370BC
    Democritis rekon that the atom had no area inside of it. He was the first to discover the atom.
  • John Dalton

    Dalton Discovered
    1) All matter is made of atoms. Atoms are indivisible and indestructible.
    2) All atoms of a given element are identical in mass and properties
    3) Compounds are formed by a combination of two or more different kinds of atoms
    4) A chemical reaction is a rearrangement of atoms
  • J.J Thompson

    He describes atoms like their a plum pudding or raising cake the atom has heaverliy positive pudding with the light negatively charged electrons embedded in it.
  • Philip Lenard

    He described atoms as mainly empty space filled with fast moving neutral particles he called dynamides were made of a heavier positive particle joined with a negative electron.
  • Ernest Rutherford

    He experiments radioactive particles he describes the nuclear atom his model of the atom had a tiny very dense positively changed nucleus about 1 10 thousand the diameter of the atom the very tiny negatively changed electrons orbited around the nucleus like tiny planets.
  • Niels Bohr

    He applies his own ideas to the electrons of the rutherford nuclear atom. His model has the electron in orbit where they are only able to exist at very definite positions with a very definite energy. The uses quantum theory which impiles that particles have set amounts of energy
  • James Chadwick

    A new model was developed from previous ideas but with changes based on the contributions of several scientists over the years. The nucleus is where most of the mass of an atom is found and contains the protons and neutrons. The number of protons in the nucleus determines what element the atom is. The electrons exist in very definite areas around the nucleus. The movement of electrons are difficult to show on a diagram as they take up an area of space, and don't have a set orbit like the Bohr.