development of the model of the atom

• what sub atomic particle was discovered first

  electron
• before electrons where discovered, was it thought that atoms could be divided

  no
• before electrons were discosvred, atoms were thought to be what

  tiny spheres
• what model did the discovery of the electron lead to

  plum pudding model
• what was the plum pudding model

  that the atom was a ball of positive charge with negative electrons embedded in it
• what model replaced the plum pudding model

  nuclear model
• what experiment led to idea that mass of the atom was concentrated in the centre

  alpha scattering experiment
• what would happen with the alpha particle experiment if the plum pudding model was correct

  expect particles to pass straight through or slightly deflected
• what was observed in the alpha scattering experiment

  alpha particles where fired at a thin sheet of gold. Most of the particle passed through with some deflected more than expected and some deflected backwards
• what model replaced the plum pudding model

  nuclear model, have a positively charged nucleus where most of the mass is concentrated and most of the atom is empty space
• who led to the idea that electrons are in orbitals/shells

  Niels Bohr
• what order where the sub atomic particles discovered

  electron, proton the neutron
• who provided evidence for the existence of neutrons within the nucleus

  Chadwick (about 20 years after the nucleus idea was accepted)
• what are the differences between the plum pudding model and the nuclear model

  plum - single ball of positive charge, electrons in random positions, no nucleus, no neutrons * nuclear - positive centre/nucleus, electrons in fixed positions, has a nucleus, has neutron
• what did Bohr suggest about the arrangement and movemnt of electrons

  electrons orbit the nucleus in shells that are a fixed distance from the nucelus. Electrons can only be found in these shells
• what particle was discovered as the nucleus was found to be positive

  proton