<P> The initial discovery was made by Hans Geiger and Ernest Marsden in 1909 when they performed the gold foil experiment in collaboration with Rutherford , in which they fired a beam of alpha particles ( helium nuclei ) at foils of gold leaf only a few atoms thick . At the time of the experiment , the atom was thought to be analogous to a plum pudding ( as proposed by J.J. Thomson ) , with the negatively - charged electrons ( the plums ) studded throughout a positive spherical matrix ( the pudding ) . If the plum - pudding model were correct , the positive `` pudding '' , being more spread out than in the correct model of a concentrated nucleus , would not be able to exert such large coulombic forces , and the alpha particles should only be deflected by small angles as they pass through . </P>
<P> The initial discovery was made by Hans Geiger and Ernest Marsden in 1909 when they performed the gold foil experiment in collaboration with Rutherford , in which they fired a beam of alpha particles ( helium nuclei ) at foils of gold leaf only a few atoms thick . At the time of the experiment , the atom was thought to be analogous to a plum pudding ( as proposed by J.J. Thomson ) , with the negatively - charged electrons ( the plums ) studded throughout a positive spherical matrix ( the pudding ) . If the plum - pudding model were correct , the positive `` pudding '' , being more spread out than in the correct model of a concentrated nucleus , would not be able to exert such large coulombic forces , and the alpha particles should only be deflected by small angles as they pass through . </P>
what was the source of alpha particles in rutherford 's experiment
what was the source of alpha particles in rutherford 's experiment
helium nuclei
helium nuclei