Answer:
Mass of an atom is concentrated in a positively charged core called the nucleus.
Step-by-step explanation:
Rutherford gold foil experiment expanded our understanding of the structure of an atom. When positively charged alpha particles were bombarded against a thin gold foil, Rutherford observed that majority of particles passed through the foil undisturbed whereas a small percentage retraced their path.
There were two main conclusions from the experiment:
-Since most alpha particles simply passed through undeviated this suggested that majority of the space inside the atom is empty
- Also, since some of them completely bounced back this suggested that there is a positively charged core in which the mass of the nucleus is concentrated.