Timeline of the Atom

  • Energy levels

    First proposed by early indian and greek philosophers. In the 17th and 18th century, chemists showed that certain substances couldn't be broken down any further by chem. methods. During the 19th and 20th century, physics discovered particles inside the atom, showing that the atom was divisible.
  • Electrons

    The electron is a fundemental subatomic particle that was identified and assigned the negative charge in 1897 by John Joesph Thompsan and his team of brithish physicists. It was discoverd by using cathode rays, Mass= 9.11 x 10^-31
  • Nucleus

    Nucleus was discoverd in 1911, as a result of ernest rutherfords interception of the famous 1909 Rutherford expeirement performed by nans geiger and ernest marsden, under the direction of Rutherford. Discovered through the gold foil expeirement.
  • Protons

    Positive electric charge. Found in the nucleus along with neutrons. protons = electrons = atomic number. Discoverd in 1918 by Ernest Rutherford.
    Mass= 1.66 x 10^-27kg
  • Neutrons

    Discovered by James Chadwick. Neutral charge. Mass= slightly larger than a proton. Discovered when James performed a series of experiments. He suggested that the new radiation consisted of uncharged particles of the mass of a proton, he than called them neutrons.
  • Period: to