1. Its all about the Electron

2. Bohr’s Model Planetary model Electrons follow a spherical path around the nucleus called Orbits –Known as Energy levels –Has definite energy –Quantized/Discrete Weblink: Orbits

3. Uncertainty Principle Proposed: Werner Heisenberg (1927) States: It is impossible to determine simultaneously the position and velocity of an electron or any other particle. Implication: We speak of probability of finding an electron in a certain region. Example: Students in the class

4. Quantum Theory Probability is a statistical/ mathematical term = involve equations The mathematical description of the behavior of electrons/small particles is called Quantum Theory. Proposed: Erwin Schrödinger (1926) We will not look at the equations, just the results of it.

5. Main Result Electron occupy a certain region of space about the nucleus This 3-dimensional region around the nucleus is called an orbital. Weblink:

6. Quantum Numbers There are 4 dimensions to the pattern of electrons. They are called Quantum Numbers Energy level (n = 1,2,3,4, etc.) Sublevel (l = s,p,d,f, etc.) Orbital (m l = x,y,z,xy,z 2, etc.) Spin (m s = +1/2= or -1/2= )

7. Energy Level, n Principal Quantum Number Represents the main energy levels In the Periodic Table, they represent the Periods Values: Integers from 1 and above.

8. Sub-Energy Level, l Angular Momentum Quantum Number Represents the shape of the orbital Values: Integers from 0 to n-1. Energy LevelSublevel 10(s) 20(s), 1(p) 30(s), 1(p), 2(d) 40(s), 1(p), 2(d), 3 (f)

9. Orbitals, m l Magnetic Quantum Number Represents the orientation of each orbital in space. Value: Integers from -l to +l SublevelOrbitals 00 1-1, 0, +1 2-2, -1, 0, +1, +2 3-3, -2, -1, 0, +1, +2, +3

10. Spin, m s Spin Quantum Number Represents the spin of the electron Values: +1/2 (spin up) and -1/2 (spin down) Every orbital can have a maximum of 2 electrons (one spin up and one spin down)

11. Principles on Orbital Filling Aufbau Principle Pauli's Exclusion Principle Hund's Rule

12. Aufbau Principle Electrons enter orbitals of lowest energy available. Refer to an aufbau diagram to find which sublevel is lowest. (Notice the overlapping of sublevels that happens at higher levels.)

13. Pauli Exclusion Principle If two electrons are in a single orbital, they must have opposite spin. (A box can have 0, 1, or 2 electrons:) = 0 e - = 1 e - = 2 e -

14. Hund's Rule If the orbitals being filled have the same energy, electrons will spread out rather than pair up (separate electrons with up spin). 1s 2s 2p

15. Orbital Diagram 1s 2s 2p 3s 3p 3d = H= H = He = N

16. Orbital Diagram 1s 2s 2p 3s 3p 3d = O= O = F = Na