<P> The Geiger--Marsden experiment (s) (also called the Rutherford gold foil experiment) were a landmark series of experiments by which scientists discovered that every atom contains a nucleus where all of its positive charge and most of its mass are concentrated . They deduced this by measuring how an alpha particle beam is scattered when it strikes a thin metal foil . The experiments were performed between 1908 and 1913 by Hans Geiger and Ernest Marsden under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester . </P> <P> The popular theory of atomic structure at the time of Rutherford's experiment was the "plum pudding model". This model was devised by Lord Kelvin and further developed by J.J. Thomson . Thomson was the scientist who discovered the electron, and that it was a component of every atom . Thomson believed the atom was a sphere of positive charge throughout which the electrons were distributed, a bit like plums in a Christmas pudding . The existence of protons and neutrons was unknown at this time . They knew atoms were very tiny (Rutherford assumed they were in the order of 10 m in radius). This model was based entirely on classical (Newtonian) physics; the current accepted model uses quantum mechanics . </P>

When did the gold foil experiment take place