1. THE ATOM! BUILDING BLOCKS OF MATTER

2. Rutherford! ► The gold foil experiment ► Shot alpha particles (helium nuclei) at gold foil 4 Mass number charge 2+

3. 0.3% of the time the alpha particle bounced back 2.7% of the time the alpha particle was deflected 97% of the time the alpha particle went straight through Lead box containing alpha particle source Gold foil Scintillation screen

4. Turn foil so you are looking at the edge. Then magnify!

5. Cross section of gold foil (Magnified x10 12 ) Alpha particle source

6. Rutherford’s Results ► Most of the atom is?  Empty space ► In the center of the atom is?  Nucleus ► With a charge of ?  Positive (due to PROTONS, the second particle)

7. The Third Particle ► Rutherford’s co-worker James Chadwick discovered the NEUTRON! ► The NEUTRON has a ________charge. NEUTRAL

8. If its mostly empty space then how are things solid?

9. 1Protons and 1Neutron Relative Mass: Animal analogy 1 amu (atomic mass unit) 2 amu (atomic mass unit) p+p+ n0n0 electron

10. Properties of Subatomic Particles ParticleSymbolLocationCharge Mass (amu) Electron e-e-e-e- Electron Cloud Negative11840 Proton p+p+p+p+NucleusPositive1 Neutron n0n0n0n0NucleusNeutral1

11. Atomic Number

12. Atomic Number = # of Protons = # of Electrons =

13. Practice Write down the symbol, NAME, atomic number, protons, and electrons for the following. 1. W 2. Au 3. U 4. Fr 5. Dy 6. 34 p + 7. 100 e - 8. Atomic number 11 9. 50 p + 10. 47 e -