1. John Dalton (b. Sept. 6, 1766, d. July 27, 1844)
He said that all matter is made up of tiny particles called atoms.
These atoms are indestructible. (no smaller particles exist)

2. MODELS OF THE ATOM
Term 1

3. Aristotle ( B.C.)
Matter is made of four elements: air, earth, fire, and water.
He believed that matter was continuous.
A magic knife could cut forever and it would still produce smaller and smaller pieces of substances.

4. Democritus (b.c. 460 BC; d. c. 370 BC)
He believed that matter is discontinuous.
He imagined atoms as indivisible spheres.
He coined the word “atomos” which means indivisible.

5. Atoms of the same element have the same size and mass while atoms of different elements have different sizes and mass.

6. J.J. Thomson (b. Dec. 18, 1856, England d. Aug. 30, 1940)
He said that: atoms are uniform spheres of positively charged matter in which electrons are embedded.
His model was called the "Raisin in the Cake Model" or the "Plum Pudding Model"

7. Thomson discovered the proton.
Protons (+) are positively charged.
Electrons (-) are negatively charged.
Atoms are neutral because they have same number of electrons and protons.

8. Science is not a collection of facts
Science is not a collection of facts. It is an ongoing process that attempts to remain in step with the latest research. That is why scientists sometimes change their minds.