1. Orbital Diagrams and Electron Configurations Vocabulary: 1.Electron configuration 2.Aufbau Principle 3.Pauli Exclusion Principle 4.electron spin 5.Hund’s Rule 6.Orbital diagram Paul Klee, Greeting, 1922. American.

2. Subshells We’ve talked about the different orbitals (subshells) that give us the probable location of electrons of various energy states. But how do we know which subshell any one electron will occupy? Should it go in an s, p, d, or f orbital? And which energy level? Luckily there are 3 rules to guide our understanding of the position of ground state electrons in an atom.

3. The rules: 1. The Aufbau Principle: Electrons fill orbitals with the lowest energy first. “Aufbau” is German for “Building up.”

4. The rules: To follow the Aufbau principle, you must know the order of orbital energy. The following chart will help you with this order: 1 st Energy level1s There is only an s orbital on the 1 st energy level.

5. The rules: To follow the Aufbau principle, you must know the order of orbital energy. The following chart will help you with this order: 1 st Energy level1s 2 nd Energy level2s 2p There are only s and p orbitals on the 2 nd energy level.

6. The rules: To follow the Aufbau principle, you must know the order of orbital energy. The following chart will help you with this order: 1 st Energy level1s 2 nd Energy level2s 2p 3 rd Energy level3s 3p 3d There are only s, p, and d orbitals on the 3 rd energy level.

7. The rules: To follow the Aufbau principle, you must know the order of orbital energy. The following chart will help you with this order: 1 st Energy level1s 2 nd Energy level2s 2p 3 rd Energy level3s 3p 3d 4 th Energy level4s 4p 4d 4f The 4 th, 5 th, 6 th, and 7 th energy levels contain all 4 types of orbitals (although you will not ever use the 6f, 7d, or 7f orbitals.) 5 th Energy level5s 5p 5d 5f 6 th Energy level6s 6p 6d 6f 7 th Energy level7s 7p 7d 7f

8. The rules: Sadly, the order of increasing energy does not follow left to right, top to bottom on this chart. Instead you need to add some arrows to help with the order. 1 st Energy level1s 2 nd Energy level2s 2p 3 rd Energy level3s 3p 3d 4 th Energy level4s 4p 4d 4f 5 th Energy level5s 5p 5d 5f 6 th Energy level6s 6p 6d 6f 7 th Energy level7s 7p 7d 7f Start here

9. The rules So following the chart, the order of the orbitals in increasing energy is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p.

10. 2. The Pauli Exclusion Principle: Only two electrons can occupy each orbital, but each must have opposite spin. The rules Wolfgang Pauli (Austria): Nobel prize in Physics, 1945

11. Spin refers to a magnetic field created by an electron. Two electrons in the same orbital must have opposite spin meaning they have opposite magnetic field orientation. We’ll represent this using an up arrow for an electron with + spin and a down arrow for an electron with – spin.  = electron with positive spin  = electron with negative spin The rules

12. 3. Hund’s Rule: If two or more orbitals of equal energy are available, electrons will occupy them singly before filling them in pairs. The rules Friedrich Hund (German)

13. So for example, if you are placing 4 electrons into the 2p orbitals, they would fill in the following order due to Hund’s Rule: The rules 2p __ __ __ correct incorrect

14. So let’s see the rules in action! Draw the orbital diagram for carbon (6 electrons). 1s ___ Rule 1: Use chart to fill lowest energy orbitals first. Rule 2: Two electrons in each orbital with opposite spin. 2s ___2p ___ ___ ___ 3 lines because there are 3 types of p-orbitals. Rule 3: Fill orbitals of equal energy 1 at a time and then pair up.

15. So let’s see the rules in action! Draw the orbital diagram for carbon (6 electrons). 1s ___ Rule 1: Use chart to fill lowest energy orbitals first. Rule 2: Two electrons in each orbital with opposite spin. 2s ___2p ___ ___ ___ The six arrows represent the positions of the six electrons in a ground state carbon atom. Rule 3: Fill orbitals of equal energy 1 at a time and then pair up.

16. So let’s see the rules in action! Draw the orbital diagram for carbon (6 electrons). 1s ___ Rule 1: Use chart to fill lowest energy orbitals first. Rule 2: Two electrons in each orbital with opposite spin. 2s ___2p ___ ___ ___ We can show this orbital diagram in a more abbreviated form called an electron configuration. Rule 3: Fill orbitals of equal energy 1 at a time and then pair up.

17. So let’s see the rules in action! Draw the orbital diagram for carbon (6 electrons). 1s ___ Rule 1: Use chart to fill lowest energy orbitals first. Rule 2: Two electrons in each orbital with opposite spin. 2s ___2p ___ ___ ___ 1s 2 Rule 3: Fill orbitals of equal energy 1 at a time and then pair up. 2s 2 2p 2 This is the electron configuration for carbon.

18. 1s __ 2s __ 2p __ __ __ 3s __ 3p __ __ __ 3d __ __ __ __ __ 4s __ 4p __ __ __ 4d __ __ __ __ __ Let’s try another one. Draw the orbital diagram and write the electron configuration for iron: 26 electrons. Electron Configuration: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6

19. Try one on your own. Draw the orbital diagram and write the electron configuration for rubidium: 37 electrons.

20. 1s __ 2s __ 2p __ __ __ 3s __ 3p __ __ __ 3d __ __ __ __ __ 4s __ 4p __ __ __ 4d __ __ __ __ __ 5s __ Try one on your own. Draw the orbital diagram and write the electron configuration for rubidium: 37 electrons. Electron Configuration: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1