1. ATOMIC THEORY

2. WHAT IS AN ATOM? What makes the elements on the Periodic Table different from each other? What is the name for the center of an atom? What is contained in the nucleus? What type of electrical charges do protons, neutrons, and electrons have?

4. PHILOSOPHY Democritus (460-370 BC) Lived in Greece Studied natural philosophy Loved to travel Worked with his teacher Leucippus All matter is made up of invisible, indestructible particles called atoms Atom comes from “atomos”, Greek for “indivisible” Lacked scientific evidence to back up his beliefs Model lasted a long time!

5. DALTON & THE ATOM English chemist, meteorologist, & physicist 1766-1844 Started out as a teacher at a Quaker school Moved to Manchester where he had access to laboratories and an intellectually stimulating environment Started his experiments that led to the atomic theory with his basis in meteorology

6. DALTON’S ATOMIC THEORY 1.All matter is made up of indivisible and indestructible particles called atoms 2.All atoms of the same element have identical mass & properties 3.Two or more different types of atoms combine to form compounds 4.A chemical reaction is a rearrangement of atoms

7. J.J. THOMSON 1856-1940 In 1897 he discovered the electron using cathode ray tube From this, he created “plum pudding” model

8. RUTHERFORD 1871-1937 Atom contains a nucleus The positive particles and the majority of the mass is located in the nucleus Used the gold foil experiment to determine this

9. GOLD FOIL EXPERIMENT