History of the atom

• The modern model of the atom Has developed overtime
• ideas about the model of the atom have changed over time because new experimental evidence leads to scientific models being changed or replaced
• John Dalton suggested that items were tiny spheres that could not be divided electrons have not been discovered yet
• JJ Thompson discovered electrons he then went onto suggest the plum pudding model. This was the idea that the atom was a ball of positive charge with negative electrons embedded in it . the discovery of the electron led to this new model.
• Particles

  • Undeflected
  • Deflected
• O was Undeflected particles, this proves that most of the atom was empty space
• Deflected particles, this proves that the nucleus was positive
• Returned particles

  • Concentrated mass in the centre of the atom
• This proves that there was a small concentrated mass in the centre of the atom
• Alpha particle scattering

  Experiment that led to the conclusion that the mass of the centre (nucleus) was concentrated and charged
• Niels Bohr

  Adapted the plum pudding model by suggesting that electrons orbit the nucleus at specific distances
• James Chadwick

  Went on to prove the existence of neutrons, which will show up in isotopes
• Models were rejected, modified and evidence as new evidence became available
• Describe one way in which Thomson’s model of the atom was different from rutherford . The Rutherford model is a nucleus surrounded by empty space. but a Thompson model was a positive ball atom charge with negative electrons embedded in it.
• Explain how the paths of the alpha particles were used to develop the nuclear model of the atom. Some alpha particles went straight through so this tells us that the nuclear model had empty space.
• Atomic particles are protons neutrons electron relative charge of protons is plus one relative charge of nutrients is neutral. Zero relative charge of electrons is minus one relative mass protons is one relative mass of neutrons is one relative mass of electron one over 1836 location of protons in the nucleus location of neutrons is in the nucleus of electrons is in the energy levels shells.
• The nucleus is around 1000 times smaller
• in an atom the number of electrons is equal to the number of protons in the nucleus
• this means that Adam has no overall electrical charge