Question

how was it shown that an atom has a lot of empty space within it ?

Answer 1

Atoms has lot of empty spaces was shown by Rutherford's experiment. Rutherford bombarded a thin foil of metal as Gold nearly 100 mm thick, with a beam of fast moving α-particles. The source of alpha particle was Radium, which is a radioactive substance and it was kept in a lead block in which slits were used to get fine beam of α-particles.

The gold foil was plated with Zinc sulphide screen so that when the α-particles strike over it at any place a light flash is given out.

It was observed that Most of the α-particles passed foil without deflecting which shows that an atom has lot of empty space inside it.