Answer: the atom is the smallest known particle of matter.
Step-by-step explanation:
Postulates of Dalton's atomic theory:
Atom are indivisible and are the smallest constituents of matter.
Atoms of same element have similar mass.
Atoms of different elements have different mass.
Elements combine with each other in whole number ratios to form compounds.
Thomson found the negatively charged particles called electrons and told they are embedded in a soup of positively charged sphere.
Thus the part of dalton's theory that thomson's findings dispute is Atom are indivisible and are the smallest constituents of matter.