atomic structure,isotopes

• what is an electron?

  Subatomic particle which has a charge of -1 and a mass of 1/1836 (almost 0) electrons are located in the shells of an atom
• what is a neutron?

  an uncharged subatomic particle with a charge of 0 and a mass of 1. the neutrons are located in the nucleus
• what is a proton?

  a subatomic particle with a charge of +1 and mass of 1 it is found in the nucleus of an atom
• what is an isotope?

  An isotope is a variant of an element that has the same number of protons but a different number of neutrons in its nucleus.
• what is an ion?

  An ion is an atom or molecule that has gained or lost electrons, resulting in a positive or negative charge.
• describe the plum pudding model

  After discovering the electron in 1897, J J Thomson proposed that the atom looked like a plum pudding.he suggested that the atom consisted of positive sea with a lot of negative electrons stuck in it
• what was the outcome of Rutherfords experiment?

  It was thought that the alpha particles could pass straight through the thin foil If the plum pudding model had been correct then all of the fast, highly charged alpha particles would have whizzed straight through undeflected. although...

  • most of the alpha particles went straight through the foil
  • a small number of alpha particles were deflected by large angles as they passed through the foil
  • a very small number of alpha particles came straight back off the foil
• what was Rutherfords alpha particle scattering experiment?

  The existence of the nucleus was discovered by Rutherford through the α scattering experiment, where beams of α particles, which struck a very thin sheet of gold foil, defected from their path.
• what did the number of alpha particles coming back suggested?

  • the very small number of alpha particles coming straight back suggested that the positive charge and mass are concentrated in a tiny volume in the atom (the nucleus) - the tiny number doing this means the chance of being on that exact collision course was very small, and so the 'target' being aimed at had to be equally tiny
• why was gold used in Rutherfords experiment?

  Gold was used because it was the only metal that could be rolled out to be very, very thin without cracking
• why it is important that Rutherfords experiment happened in a vacuum chamber?

  The vacuum is important because any deflection of the alpha particles would only be because of collisions with the gold foil and not due to deflections off anything else.
• what are alpha particles and why were they used in the gold foil experiment?

  Alpha particles are a form of nuclear radiation with a large positive charge. since they are positively charged they will repel against the positive nucleus
• why was James Chadwicks discovery of the neutron important?

  Chadwick's findings were pivotal to the discovery of nuclear fission, and ultimately the development of the atomic bomb
• how did Chadwick discover the neutron?

  Chadwick used a version of Rutherford's experiment, using a sheet of beryllium and a paraffin block instead of gold foil.

  In doing so he discovered the proton-sized neutral particle - now known as the neutron.