2. NOTES: 5.2 – Electron Configurations

3. Electron Configuration! VIDEO

4. Electron Configurations ● The quantum mechanical model of the atom predicts energy levels for electrons; it is concerned with probability, or likelihood, of finding electrons in a certain position.

5. Electron Configurations ● Electron configurations are the ways in which electrons are arranged in various orbitals around the nuclei of atoms

6. Electron Configurations ● Regions where electrons are likely to be found are called orbitals. EACH ORBITAL CAN HOLD UP TO 2 ELECTRONS!

7. ● Describes the energy level that the electron occupies ● n = 1, 2, 3, 4… ● The larger the value of n, the farther away from the nucleus and the higher the energy of the electron. Principal Quantum Number (n) n = 1 n = 2 n = 3 n = 4

8. Sublevels ( l ) ● The number of sublevels in each energy level is equal to the quantum number, n, for that energy level. ● Sublevels are labeled with a number that is the principal quantum #, and a letter: s, p, d, f (ex: 2p is the p sublevel in the 2 nd energy level)

9. Sublevel# OrbitalsMax # elec. s12 p36 d510 f714 RECALL:

10. Summary of Atomic Orbitals Principal Quantum Number # of Energy Sublevels Type of Sublevel # of Orbitals Total # of Electrons 11s12 22s, p48 33s, p, d918 44s, p, d, f1632

11. Electron Configurations: ● The way in which electrons are arranged in atom follow three rules:

12. Rule #1: Aufbau Principle ● electrons enter orbitals of lowest energy first ● the orbitals within the same sublevel (e.g. the 3 orbitals in the 3p sublevel) are always of equal energy ● the s sublevel is always the lowest-energy sublevel ● in some cases, the energy levels within a principal energy level may overlap with energy levels in a different principal energy level

13. Electron Configurations

14. Start Filling Here!

15. Rule #2: Pauli Exclusion Principle ● an atomic orbital can describe (contain) at most two electrons ● to occupy the same orbital, 2 electrons must have opposite “spins” (1 is clockwise, 1 is counterclockwise) ● opposite spins are shown as ↑↓ or with oppositely charged “spin quantum numbers”

16. Spin quantum number (m): ● Labels the orientation of the electron ● Electrons in an orbital spin in opposite directions; these directions are designated as +½ and -½

17. Rule #3: Hund’s Rule ● Orbitals of equal energy are each occupied by one electron before any pairing occurs.  Repulsion between electrons in a single orbital is minimized ● All electrons in singly occupied orbitals must have the same spin. ● When 2 electrons occupy an orbital they have opposite spins.

18. Orbital Diagrams: ● Each orbital is represented by a box. ● Each electron is represented by an arrow. Ne

19. Orbital Diagrams ● hydrogen ● helium ● carbon 1s 2s2p

20. Write the electron configuration for the following: ● Fluorine ● Phosphorus: ● Potassium:

21. Electron Configurations

22. Write the electron configuration for the following: ● Fluorine: 1s 2 2s 2 2p 5 ● Phosphorus: ● Potassium:

24. Write the electron configuration for the following: ● Fluorine: 1s 2 2s 2 2p 5 ● Phosphorus: 1s 2 2s 2 2p 6 3s 2 3p 3 ● Potassium:

25. Write the electron configuration for the following: ● Fluorine: 1s 2 2s 2 2p 5 ● Phosphorus: 1s 2 2s 2 2p 6 3s 2 3p 3 ● Potassium: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1

26. Electron Configurations

27. Complete electron configurations: ● helium ● boron ● neon ● aluminum ● uranium

28. Electron Configurations

30. Complete electron configurations: ● helium ● boron ● neon ● aluminum ● uranium 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 4 1s 2 2s 2 2p 6 3s 2 3p 1 1s 2 2s 2 2p 6 1s 2 2s 2 2p 1 1s 2

31. Abbreviated electron diagrams: ● helium ● boron ● aluminum ● cobalt ● uranium

32. Electron Configurations

34. Abbreviated electron diagrams: ● helium ● boron ● aluminum ● cobalt ● uranium 1s 2 [He]2s 2 2p 1 [Ne]3s 2 3p 1 [Ar]4s 2 3d 7 [Rn]7s 2 5f 4

35. Exceptional Configurations: ● Consider: Cr and Cu ● By following the Aufbau diagram for filling energy levels, you would assign the following electron configurations: Cr: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 4 4s 2 Cu: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 9 4s 2 However, the correct configurations are…

37. Exceptional Configurations: ● Consider: Cr and Cu ● Correct configurations: Cr: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 1 Cu: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 1 **filled energy sublevels (3d 10 ) are more stable than partially filled sublevels (4s 1 ) **half-filled levels can be more stable than other configurations (as in Cr)