Presentation on theme: "What are important discoveries related to the structure of an atom?"— Presentation transcript:
What are important discoveries related to the structure of an atom?
Three sub-atomic particles: Atom – basic unit of matter Element –substance consisting of one type of atom Compound – substance consisting of two or more different atoms
Democritus The Laughing Philosopher - Matter composed of atoms (tiny indestructible units) - No experiments, Little evidence - Smooth (sweet) and sharp (sour) atoms
John Dalton 1808 Dalton's Atomic Theory 1) Matter is made of atoms which are indivisible and indestructible. 2) All atoms of an element are identical in mass and properties. 3) Compounds are formed by two or more different kinds of atoms coming together. 4) A chemical reaction is a rearrangement of atoms.
JJ Thomson 1897 Lots of positive space with negative clusters Cathode Ray Experiment Discovered electrons Plum Pudding Model Chocolate Chip Muffin