The scientist thought that the
atom was the smallest particle in the universe is John Dalton. The answer is
letter B. 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. J.J.
Thompson discovered the electrons in the atom. Ernest Rutherford discovered the
half – life of an atom and Neils Bohr explain the quantum mechanics.
