Answer:
Step-by-step explanation:
The atom is the smallest particle of matter.
As we know atom is not the smallest particle of an element, it is even compose of electron, neutron and proton.
This was not then discovered. Now Marie Curie was a researcher who worked on radioactivity of an element and discovered new elements.
As per theory of radioactivity, It is a property of unstable atomic nuclei. In this process it releases energy in form of radiation.
If Dalton theory that atom is the smallest particle would have been true then definitely it is impossible for Marie Curie to discover new elements as her theories and work were based upon study of different particle of atoms.