THE SUBATOMIC PARTICLES AND THE STRUCTURE OF THE ATOM

• ELECTRON:

  • Cathode-Ray Tube Experiment (Discovery of Electrons) (J.J. Thomson)

  -cathode-ray tube is a glass tube from which most of the air has been evacuated

  *cathode - negatively charged plate - emits an invisible ray that is drawn to the anode

  *anode - positively charged plate - the invisible ray passing through a hole and travelling to the other end of the tube

  • Oil Drop Experiment (Quantify the charge of electron) (Robert Millikan)
  • The Plum Pudding Model (Raisen bread model) (J.J. Thomson)
• PROTON AND THE NUCLEUS:

  • Gold Foil Experiment (Alpha Scattering Experiment)(Ernest Rutherford)

  -majority of particles penetrated the foil either undeflected or with a slight deflection or deflected at large angle or bounced back in the direction of its source

  • Nuclear Model of an Atom

  -nucleus in the center

  -protons - positively charged particles
• NEUTRON:

  • Alpha Particle and Beryllium Experiment (James Chadwick)

  Neutrons - electrically neutral particles, a mass slightly greater than that of protons
• Dalton's Atomic Theory:

  Postulate 1 : Elements are compound of extremely small particles (atoms)

  Postulate 2: All atoms of an element are identical, same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements

  Postulate 3: Compounds are composed of atoms of more than one element and ratio (integer or simple fraction)

  Postulate 4: A chemical reaction involves only the separation, combination, rearrangement of atoms. There is no creation or destruction.