1. The Atom

2. Aristotle – the four basic elements -Earth -Air -Water -Fire

3. Democritus -Follower of Leucippus -An Atomist -Coined the word atomos meaning uncuttable or the smallest particle of matter

4. 2000 years later John Dalton – School Teacher Five main points of Dalton's atomic theory -The atoms of a given element are different from those of any other element; the atoms of different elements can be distinguished from one another by their respective relative atomic weights. -All atoms of a given element are identical. -Atoms of one element can combine with atoms of other elements to form chemical compounds; a given compound always has the same relative numbers of types of atoms. -Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical reaction simply changes the way atoms are grouped together. -Elements are made of tiny particles called atoms.

5. Daltons Model of the Atom

6. Cathode Ray Tube

7. Plum Pudding Model of the Atom JJ Thompson

8. Gold Foil Experiment – Ernest Rutherford

9. Rutherford’s Model of the Atom

10. ParticleSymbol Relative ChargeMass (kg) Mass NumberLocation electrone-e- 9.109x10 -31 0 Around Nucleus protonp+p+ +11.673x10 -27 1Nucleus neutronn0n0 01.675x10 -27 1Nucleus

11. Atomic Number: The number of protons in the nucleus of an atom Mass Number: The total number of protons and neutrons on a nucleus Atomic Number Symbol Atomic Mass

12. Isotope: Atoms of the same element that have different masses