1. Inside the Atom

2. Early Ideas Electrons were found early on and they knew that they had a negative charge Pudding model: –Electrons are imbedded in a matrix of positive charge much like raisins in a bread pudding

3. Rutherford’s Experiment Directed a stream of α (alpha) particles at a thin foil of gold –α particles have a positive charge and come from radiation

6. Rutherford’s Experiment Directed a stream of α (alpha) particles at a thin foil of gold –α particles have a positive charge and come from radiation Showed that there is a small nucleus that is positively charged Later found that it contains most of the mass –And contains protons and neutrons

7. Subatomic particles Relative Charge Relative Mass Location Electron0.00055? Proton+11.00727? Neutron01.00867?

8. Bohr Model Electrons are in circular orbits around nucleus –Like planets around the sun

9. Present Model Electrons are in orbits around nucleus Orbits are not circular or elliptical We can only tell where the electrons are the most likely to be More like electron clouds –Can still think of them as planetary orbits –We will draw them that way

10. Atomic Number Number of protons – always an integer Unique for each element Also number of electrons if no charge (neutral) Be careful not to confuse with atomic mass

11. Mass Number Number of nucleons (protons and neutrons) Is not unique for each element # of neutrons = mass# - atomic# Not given on periodic table or element lists Do not confuse with Atomic Mass

12. Isotopes Same element but different mass number (different number of neutrons) Have same atomic number Chemical behavior determined by number of electrons so same chemical behavior Nomenclature: X OrX-M# M# A#

14. Atomic Mass Is a relative mass – call Carbon-12→12.00 Uses “amu” as units – atomic mass units Calculated for average atom if has isotopes Weighted average by percent natural abundance

15. Electron Energies Energies, velocities, and distance from nucleus are all proportional Continuous (Newtonian) description doesn’t work Quantum mechanics was developed to explain –Deals with probabilities and packages

16. Electron Energies Continuous ModelQuantum Mechanics

17. H7 – C3 4, 7 - 12, 14, 15, 50 - 54

20. Electron Shells Contain all electrons at approx. same energy and distance out. Shell Number designation Electron capacity (2n*n) 1 st 1 2 2 nd 28 3 rd 318 4 th 432 5 th 550

22. Valence Electrons Only with representative elements Electrons in outer shell –Farthest out –Most loosely held Most likely to be involved in a chemical reaction