Answer:
In 1910, Rutherford and his coworkers were studying the angles at which alpha particles were scattered as they passed through a thin gold foil. Most particles passed through undeflected, though a few were found to be scattered at large, some even in the direction they had come. This meant they had collided with an object much more massive than the particle itself, but so small that only a few aplha particles encountered them. Showing that the atom was composed of a small dense massive center surrounded by low mass electrons.