Answer is: the atom is the smallest known particle of matter.
John Dalton claimed that atom is indestructible and a<span>ll atoms of a given element are identical in mass and properties.
</span>Thomson discovered electron and found the first evidence for isotopes<span> of a stable element.</span>
Thomson suggested the model of atom which was a sphere of positive matter within which electronic forces determined the positioning of the corpuscles. The corpuscles were distributed in a uniform sea of positive charge. This was so-called "plum pudding" model.
Answer: C ) Thomson