The scientist thought that the
atom was the smallest particle in the universe is John Dalton. He established
the atomic theory which consists of five; elements are made of extremely small
particles called atoms, atoms of different element have different sizes, mass
and physic – chemical properties, atoms cannot be divided further, destroyed or
created, atoms can combine to form compounds and in chemical reaction, atoms
can be combined, separated or rearranged. Hope this helps!!
