# How does the alpha-particle scattering experiment imply that the nucleus has a positive charge?

## I have a textbook which says that from the results of the 1908 alpha particle scattering experiment by Rutherford, Geiger and Marsden shows that the nucleus has a positive charge but I don't see why this has to be?

The trajectories, particularly the $\alpha$ particles that returned straight out, could not do this if they were attracted to the nucleus.
The exchange of momentum requires the forces acting on the $\alpha$ particle to be repulsive. Attractive forces would create a different distribution of trajectories.