1. Quantum Mechanical Model Or…”Electron Cloud Model” Electrons move freely within “clouds” (called orbitals) not just restricted to orbits. [http://www.gly.fsu.edu/%7Esalters/GLY1000/6_Minerals/Slide9.jpg]

2. Quantum Mechanical Model Atoms have different numbers and shapes of orbitals depending on their number of electrons. “s orbital”

3. p orbitals d orbitals

4. Quantum Mechanical Model As the energy of an electron increases, so does the quantum number (n) Each principle energy level is also split up into one or more sublevels Chart on Pg. 145 [http://www.chemistry.mcmaster.ca/esam/Chapter_4/fig4-2.jpg]

6. Quantum Mechanical Model In each orbital, only 2 electrons can exist because of electron spin Click here for an Atomic Orbital Applet

7. Electron Orbital Diagrams Show which orbitals in an atom electrons occupy. Arrows are used to represent the electrons.

8. Electron Orbital Diagrams Aufbau Principle: Electrons must “fill” lower energy orbitals before higher energy orbitals. 1s before 2s, 2s before 2p …

9. Electron Orbital Diagrams Pauli Exclusion Principle: Electrons in a orbital always move in opposite directions (spin!) Use up and down arrows.

10. Electron Orbital Diagrams Hund’s Rule: All orbitals of a certain shape must be occupied by one electron before they can be paired.

11. Electron Orbital Diagrams Example: Carbon

17. Electron Orbital Diagrams Example: Oxygen Orbital Diagrams provided by: [http://intro.chem.okstate.edu/1215/Lecture/Chapter11/Fri11216.gif]