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]

Quantum Mechanical Model

• Atoms have different numbers and shapes of orbitals depending on their number of electrons. “s orbital”

p orbitals

d orbitals

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]

Quantum Mechanical Model

• In each orbital, only 2 electrons can exist because of electron spin

Click here for an Atomic Orbital Applet

Electron Orbital Diagrams

• Show which orbitals in an atom electrons occupy.

• Arrows are used to represent the electrons.

Electron Orbital Diagrams

• Aufbau Principle:• Electrons must “fill” lower energy

orbitals before higher energy orbitals.

• 1s before 2s, 2s before 2p …

Electron Orbital Diagrams•Pauli Exclusion Principle:

Electrons in a orbital always move in opposite directions (spin!)

•Use up and down arrows.

Electron Orbital Diagrams

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

Electron Orbital Diagrams

•Example: Carbon

Electron Orbital Diagrams

•Example: Oxygen

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