1. Electron Configurations Unit 3.7 and 3.8

2. Orbitals Region outside the nucleus where the electron has the highest probability of being. Drawn with a fuzzy border like the atmosphere around earth. No defined border because there is a small chance the electron may be outside this region. The orbital pictured to the right is the 1s orbital. It is the lowest energy level for hydrogen.

3. Principal Energy Levels Remember Bohr demonstrated that hydrogen had 4 main energy levels. These energy levels are called principal energy levels. Each principal energy level can be divided into sublevels. 4 Sublevels 3 Sublevels 2 Sublevels 1 Sublevel Energy Level 1 Energy Level 2 Energy Level 3 Energy Level 4

4. Principal Energy Levels The first energy level has one sub energy level. This sub energy level is known as the 1s orbital. The 1 stands for the principal energy level and the s stands for its shape (spherical) The 1s orbital can hold 2 electrons. Remember the first floor of the “Hog Hilton” had one room that could hold two pigs. Energy Level 1 Energy Level 2 Energy Level 3 Energy Level 4 2 electrons in the 1 st principal energy level.

5. Principal Energy Level 2 The second energy level has 2 sub energy levels. 2s and 2p The 2s orbital is just like the 1s orbital but larger in size. The 2p sublevel consists of 3 orbitals. Each of the 2p orbitals holds two electrons for a total of 6. Energy Level 1 Energy Level 3 Energy Level 4 2p x 2p y 2p z 8 electrons in the 2 nd principal energy level.

6. 2p Orbitals The three 2p orbitals are “lobed” shaped. The x, y, and z tell which axis the lobes are parallel to.

7. Principal Energy Level 3 The 3 rd energy level has three sublevels: 3s, 3p and 3d. The 3s orbital is shaped like the 1s and 2s; it is just larger and further from the nucleus. The 3 p sublevel also has 3 orbitals. (3p x, 3p y, and 3p z ) They are shaped like the 2p orbitals only larger. The 3d sublevel has 5 orbitals. Each orbital can hold 2 electrons for a total of 10 electrons Energy Level 1 Energy Level 4

8. 3 rd energy level 3s3p x 3p y 3p z 2 nd energy level 1 st energy level 3d orbitals 18 electrons in the 3 rd principal energy level.

9. There are 5 3d orbitals You don’t need to know these shapes.

10. Principal Energy Level 4 The 4 th energy level has four sublevels: 4s, 4p, 4d and 4f. There is one 4s orbital, three 4p orbitals, five 4d orbitals just like the 3s, 3p and 3d orbitals except they are larger. The 4f sublevel has 7 orbitals. Each orbital can hold 2 electrons for a total of 14 electrons Energy Level 1 Energy Level 2 Energy Level 3

11. Energy Level 1 Energy Level 2 Energy Level 3 4s4p x 4p y 4p z Five 4d orbitalsSeven 4f orbitals 32 electrons in the 4 th principal energy level.

12. There are seven 4f orbitals You don’t need to know these shapes.

13. Electron Arrangements The most attractive orbital to an electron in an atom is always the 1s, because this orbital is closest to the nucleus. Hydrogen has 1 electron in this orbital so its electron configuration is: 1s 1 Helium has 2 electrons in this orbital so its electron configuration is: 1s 2 Elements with more than two electrons fill the 1s orbital first before filling higher energy orbitals.

14. Electron Arrangements Continued… The 1s orbital gets filled first, then the 2s, then the 2p, then the 3s followed by the 3p. Since lithium has 3 electrons, two can fit in the 1s orbital and the last goes in the 2s orbital. Therefore the electron configuration for lithium is:

15. Time for Electron Configuration Practice!

16. Take a Shortcut… Electron Configuration for Sulfur & Neon S (16 electrons): 1s 2 2s 2 2p 6 3s 2 3p 4 Ne (10 electrons):1s 2 2s 2 2p 6 Instead of writing out the full electron configuration for sulfur use the NOBLE GAS notation: [Ne] 3s 2 3p 4

17. Noble Gas Notation Practice: Write the regular electron configuration for boron and helium: B (5 electrons): 1s 2 2s 2 2p 1 He (2 electrons):1s 2 Now write the noble gas notation for Boron: [He] 2s 2 2p 1

18. Orbital Diagrams Orbital diagrams show all of the electrons in an atom. They are similar to the Hog Hilton drawings you made. Just like the hogs in the Hog Hilton two electrons can fit in each orbital but they must be spinning in opposite directions. We represent this on an orbital diagram as an up and a down arrow. 1s

19. Orbital Diagrams Electrons spread out as far as possible before pairing (because of repulsion). This is known as Hund’s Rule or the “Empty Bus Seat Rule” If there are 4 electrons in the p-orbital: WRONG RIGHT

20. Time for Orbital Diagram Practice!

21. Orbital Filling order What is the electron configuration for Potassium? It is actually: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 We fill up the 4s orbital before filling up the 3d orbitals. Why? ▫Because the d and f orbitals require a lot of energy to fill.

22. This make sense… Remember the periodic table you colored with the s, p, d and f blocks? We could’ve used it to guess what the last orbital for potassium would be based on its location in the periodic table. It is in the s-block. It is in the first column of the block It is in the fourth period. So it should end with: 4s 1

23. Orbital Filling Order The diagram to the right shows the order in which the orbitals get filled. Notice that the fourth energy level starts to get filled before the third energy level is completely filled. Etc.

24. Valance Electrons The definition hasn’t changed! Still the number of electrons in the highest energy level. Example: Potassium- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Core Electrons Valance Electron

25. Practice Problem Write the electron configuration for Gallium & identify the VALENCE electrons! Gallium (31 Electrons): 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 1 Core ElectronsValance Electrons Gallium has 3 total valance electrons! This makes sense because it is in group 3A!

26. Periodic Table Patterns Review s 12345671234567 d (n-1) p f (n-2)

27. Periodic Patterns Continued The “A” column numbers= number of total valance electrons. The period number= energy level (subtract for d and f) Column number within a block = number of electrons in that orbital.

28. Example: Strontium [Kr]5s 2 Second column in the block Period 5 S Block Previous Noble Gas 12345671234567

29. Practice Problem Use the patterns on the table to figure out the electron configuration for Germanium. [Ar]4s 2 3d 10 4p 2 12345671234567

30. Time for Practice!