1. Unit: Electron Configurations Writing Electron Configurations and Orbital Notations

2. After today, you will be able to… Write electron configurations in the proper long-form notation Write electron configurations in the proper long-form notation Write orbital notations for certain elements in the proper notation Write orbital notations for certain elements in the proper notation Identify elements from their electron configuration or orbital notation Identify elements from their electron configuration or orbital notation

3. Recall, an electron configuration is a method of indicating the arrangement of electrons in a particular element or ion.

4. Electrons fill the 1 st energy level before the 2 nd, before the 3 rd, etc.Electrons fill the 1 st energy level before the 2 nd, before the 3 rd, etc. Within an energy level fill s, p, d, then fWithin an energy level fill s, p, d, then f Remember for a neutral atom:Remember for a neutral atom: p+ = e- = atomic number

5. Example: Write the electron configuration for Hydrogen Hydrogen has 1e - : 1s 1 Energy Level (n) Sublevel # of electrons

6. Helium has 2e - : 1s 2 Example: Write the electron configuration for Helium

7. Lithium has 3e - : 1s 2 2s 1 Aufbau Principle: Electrons enter sublevels with the lowest energy first Example: Write the electron configuration for Lithium

8. Nitrogen has 7e - : 1s 2 2s 2 2p 3 Example: Write the electron configuration for Nitrogen

9. Magnesium has 12e - : 1s 2 2s 2 2p 6 3s 2 Example: Write the electron configuration for Magnesium

10. For elements with more than 18 electrons, sublevels are filled out of order – BUT the lowest energy sublevels are still filled first! (See energy level diagram)

11. Energy Levels Increasing Energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 7p 3d 4d 5d 6d 4f 5f

12. Example: Write the electron configuration for Potassium Potassium has 19e - : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1

13. Example: Write the electron configuration for Cobalt Cobalt has 27e - : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 7

14. How to Write Orbital Notations Uses circles to represent atomic orbitals with a label underneath to indicate sublevel and energy level –One electron = __ or –Two electrons = __ or

15. Examples… Hydrogen 1s Lithium 1s 2s Pauli Principle: Atomic orbitals can hold only 2 electrons at most and they must have opposite spins.

16. Examples… Nitrogen 1s 2s 2p Hund’s Rule: In a sublevel with more than one orbital, put one electron into each orbital before putting 2e- into any one orbital.

17. Identifying elements from the e- configurations or orbital notation… Recall, if an element is neutral: # of e- = # of p+ = atomic # Examples: 1s 2 2s 2 2p 6 = 10 e- = Neon = 11 e- = Sodium 1s 2s 2p 3s

18. H

19. He When electrons are in the same orbital they “spin” in opposite directions

20. Li

21. Be

22. B

23. C

24. N

25. O

26. F

27. Ne

28. Na

29. Mg

30. Al

31. Si

32. P

33. s

34. Notation Ne: 1s 2 2s 2 2p 6