ernst rutherford

• what is an alpa particle?

  a helium nuclei
• what is the charge of an alpha particle?

  positively charged +2, 2 neutrons and 2 protons
• observation most alpa particles travel through the foil undeflected


  interpretation the atom is mostly empty space
• observation some alpha particles are deflected at small angles?

  interpretation the nucleus is positively charged as is the alpha particle
• observation alpha particles get deflected back to where they came from?

  interpretation nucleus carries most of the atoms mass
• how did the experiment work?

  beam alpha particles directed gold foil and observed the interaction of particles with the foil caused the alpha particles to be scattered and from the scattering he deduced properties about the structure of the atom
• rutherford concluded?

  • over 99,9% of the mass of the atom was empty space
  • nucleus must be positively charged
  • the rest of the atoms volume was taken up by circling electrons
• mass of the electron is 1/2000 of the mass of a proton
• what was wrong with his model?

  according to the laws of physics the electrons would be giving off light and constantly loosing energy and therefore the atom would collapse