how were alpha particles used and founded before the gold foil experiment if we didn’t know at that time that protons and neutrons existed and we didn’t know the charge of alpha particles

Question

I understood most of the rutherford experiment except how did rutherford know the properties of alpha particles when we didn’t know about protons and neutrons .

In: Chemistry

Answer 1

We knew how to detect ionizing radiation. We also knew, that when we put a stream of radiation in an electromagnetic field, it will split into three streams. One positively charged, one negatively and one uncharged. These were called alpha, beta and gamma. Even without knowing their internal structure we could determine the charge and mass of alpha and beta, by observing how they behave in a field.