October 26, 2009

1. October 26, 2009 REMINDER: STUDY GROUP ASSIGNMENT THIS WEEK LAB THIS WEEK ELECTRON ORBITALS

2. Visible Spectroscopy

3. Heisenberg Uncertainty Principle • We can’t know both the exact location and the energy of a particle • For electrons => We know the energy, so we don’t know the location very well

4. Schrödinger’s Model of Hydrogen • Electrons act as standing waves • Wave behavior is described by a wave function: ψ • Certain wave functions are allowed • ψ2 describes the probability of finding the electron in a particular spot (aka, electron density) • Arise when wave has boundaries • Has nodes (lack of vibration at certain points) This we can measure!

5. Here’s what a probability density looks like… • (A bit simplified) …but what does it mean?

6. Orbitals • Each wave function describes a shape = Orbital • Where an electron can be found/exist • Organized into main shells and subshells • Number of orbitals is different for each subshell type: • s = 1 orbital • p = 3 orbitals • d = 5 orbitals • f = 7 orbitals Size and Energy (n=1, 2, 3, … ) Shape (s, p, d, f, … )

8. 3d ___ ___ ___ ___ ___ 3p ___ ___ ___ 3s ___ 2p ___ ___ ___ 2s ___ 3 2 1s ___ 1 ENERGY 4f ___ ___ ___ ___ ___ ___ ___ 4d ___ ___ ___ ___ ___ 4p ___ ___ ___ 4s ___ 4 • 1, 2, and 3 correspond to the major energy levels (main shells) • At the same main shell level, a p orbital will be at a higher energy than an s orbital

9. What type of orbital is this? • s • pz • dxy • dxz 10

10. Which type of orbital can’t exist? • 1px • 2px • 2s • 3dxy 10

11. NODES- Where electrons don’t go Spherical Nodes

12. Hydrogen

13. You too can play with hydrogen… http://homepages.ius.edu/kforinas/physlets/quantum/hydrogen.html

14. Quantum # Rules • There are four different quantum numbers: n, l, ml, and ms • n, l, and ml are integers • n cannot be zero • l can be 0 to n-1 • ml can be anything from –l to l • Ms can be +½ or -½

15. Quantum Numbers and Orbitals

16. Rules for filling orbitals • Pauli Exclusion Principle No two electrons can have the same 4 quantum numbers An orbital has a maximum of 2 electrons of opposite spin • Aufbau/Build-up Principle Lower energy levels fill before higher energy levels • Hund’s Rule Electrons only pair after all orbitals at an energy level have 1 electron • Madelung’s Rule Orbitals fill in the order of the value of n + l

17. Orbital Filling Order