Unit 5.4: Energy Level Diagrams

Aufbau Principle

Energy levels are filled from the lowest energy level to the higher (must be obeyed for the ground state)

• There are some exceptions to this rule

Aufbau Principle: Chromium and Copper

Instead of following the aufbau thing the electron in the 4s orbital jumps down to 3d orbital to equally space all the electrons

Aufbau Principle: Excited state

Electron will jump to a higher level to stabilize and make it equal…? FWAHT

Hund’s Rule

An electron is placed in each orbital on its own before a pair is added to it (must be obeyed for the ground state)

• To balance the energy so it isn’t at a higher energy level (due to repulsive forces) making it unstable

Energy Diagram order

1. 1s

2. 2s

3. 2p

4. 3s

5. 3p

6. 4s

7. 3d

8. 4p

Electron Configuration

1. Determine the number of electrons and the electron's position

2. Assign them ground energy levels based on the diagram 

3. Write accordingly

   • 1s² → 1= shell/energy level, s= type of orbital, 2= number of electrons in the orbital (including the orientation)

Condensed Electron Configuration

Uses the preceding noble gas (in square brackets) and then continues to write the electron configurations after that point

Periodic Blocks

Determines the electron configuration the element ends with

The different periodic blocks

1. s-block: Group 1 and 2 + Helium

2. p-block: 2nd period on the right side and periods that follow (after transition metals)

3. d-block:  Transition metals 

4. f-block: radioisotopes