How did ernest rutherford know that an atom was mostly empty space

In 1909 Ernest Rutherford suggested an experiment using alpha particles and gold leaf . The results of this experiment led to changing the understanding of atomic structure . The "new" atom was mostly empty space and constituted the nucleus. Ernest Rutherford (1871-1937) was a New Zealandborn chemist who worked with J.J.Thomson at Cambridge University , was a pupil thereof . He conducted experiments with Thomson gas ions treated with X-rays in 1898. Rutherford alpha and beta rays proved the existence of the uranium atoms .