We’re gonna take it nice and easy this first day back with a quick review of Electron Configurations and Orbital Diagrams that we left off with before we went on a week and a half hiatus. But! You can plan on having a quiz over these topics (and KLM diagrams) on Thursday.

To complete today’s assignment (the answers are posted BTW), you’ll need the following information about Orbital Diagrams. These are the rules that dictate where electrons go and how they spin.

1. Hund’s Rule: One electron is placed in each orbital of an electron shell BEFORE a second one is put in any of the shells.

• Correct: ↑↓  ↑_   ↑_  ↑_  ↑_
• Incorrect: ↑↓  ↑↓  ↑↓  __  __

2. Aufbau Principle: Each shell must be completely filled before beginning to fill the next shell

• Correct: ↑↓      ↑_   ↑_  ↑_
•              3s        3p
• Incorrect: __    ↑↓  ↑↓  ↑_
•                3s          3p

3. Pauli Exclusion Principle: Electrons in the same orbital spin in opposite directions

• Correct: ↑↓
• Incorrect: ↑↑