Subshells and Orbitals

1. Subshells and Orbitals Timberlake LecturePLUS 2000

2. Quantum Mechanics Describes the arrangement of electrons in atoms in terms of: • Main or principal energy levels (n) • Energy subshells • Orbitals (space occupied within the atom) Timberlake LecturePLUS 2000

3. Principal Energy Levels (n) Contain electrons that are • Close in energy • Similar distance from nucleus • Have values of n = 1, 2, 3, 4, 5, 6….. • Maximum number of electrons = 2n2 n =1 2(1)2 = 2 n =2 2(2)2 =8 n=3 Timberlake LecturePLUS 2000

4. Energy Levels (Shells) • A group of electrons in an atom all having the same principal quantum number (n) n = 1, 2, 3, … • The first shell (n = 1) is lowest in energy, 2nd level next and so on 1<2<3<4 • The number of electron in each shell is limited to 2n2 n = 1 2n2 = 2 n = 2 2n2 = ____ Timberlake LecturePLUS 2000

5. Energy Levels for Electrons Some possible electron transitions for the first three energy levels are shown below. The negative value means that the electron in the atom has a lower energy than a free electron Energy Level Energy, E n=3 ___________________ (-) 2.420 x 1019 J n=2 __________________ (-) 5.445 x 1019 J n=1 __________________ (-) 2.178 x 1018 J Timberlake LecturePLUS 2000

6. Learning Check S1 A. What energy change (J) takes place when an electron in a hydrogen atom moves from the first (n=1) to the second shell (n=2)? B. What energy change (J) takes place when the electron moves from the third shell to the second shell? Timberlake LecturePLUS 2000

7. Solution S1 A. What energy change takes place when an electron in a hydrogen atom moves from the first (n=1) to the second shell (n=2)? 1.634 x 10-18 J of energy must be absorbed. B. What energy change takes place when the electron moves from the third shell to the second shell? (-5.445 x 10-19J)-(2.2420 x 10-19 J) = -3.025 x 1019J will be emitted as electron falls from a higher to a lower energy state Timberlake LecturePLUS 2000

8. Subshells • Energy sublevels within energy level • All electrons in a subshell have the same energy • Designated s, p, d, f .. • Sublevel energy: s<p<d<f Timberlake LecturePLUS 2000

9. Electron Locations Main Energy Levels Sublevels n=4 4s, 4p, 4d, 4f n=3 3s, 3p, 3d n=2 2s, 2p n=1 1s Timberlake LecturePLUS 2000

10. Sublevels in n = 1,2, 3 3d n = 3 3p 3s 2p n = 2 2s n = 1 1s Timberlake LecturePLUS 2000

11. Electrons Allowed • All electrons in the same sublevel have the same energy. • All 2s electrons have the same energy. All 2p electrons have the same energy which is slightly higher than the energy of the 2s electrons s sublevel 2 electrons p sublevel 6 electrons d sublevel 10 electrons f sublevel 14 electrons Timberlake LecturePLUS 2000

12. Electron Configuration • List of subshells containing electrons • Written in order of increasing energy • Superscripts give the number of electrons Example: Electron configuration of neon number of electrons 1s2 2s2 2p6 main shell subshell Timberlake LecturePLUS 2000

13. Order of Filling • Total energy of a subshell = energy of the main shell + the subshell • The 4s energy < 3d energy 4p ___ 3d ___ (finishes the n=3 shell) 4s ___ (starts the n=4 shell) 3p ___ 3s ___ 2p ___ 2s ___ 1s ___ Timberlake LecturePLUS 2000

14. Writing Electron Configurations H 1s1 He 1s2 Li 1s2 2s1 C 1s2 2s2 2p2 S 1s2 2s2 2p6 3s2 3p4 Timberlake LecturePLUS 2000

15. Sublevel Blocks s1 s2 p1 p2 p3 p4 p5 p6 1 2 3d1 - d10 4 5 6 f1 - f14 Timberlake LecturePLUS 2000

16. Periodic Table and Electron Configuration • Find the element on the periodic table • Use the order of filling indicated across each period Groups 1-2 = s level Groups 3-8 = p level Transition = d level Lantanides = f level Timberlake LecturePLUS 2000

17. Learning Check S2 Indicate if each configuration is (1) correct or (2) incorrect for potassium. Give an explanation for selection of 1 or 2. Explain why or why not? A. 1s22s22p63s1 1 or 2 B. 1s22s22p63s23p6 1 or 2 C. 1s22s22p63s23p64s1 1 or 2 D. 1s22p83s1 1 or 2 E. 1s22s22p63s23p7 1 or 2 Timberlake LecturePLUS 2000

18. Solution E2 For phosphorus, indicate if each configuration is (1) correct or (2) incorrect. Explain why or why not. A. 2, 2, 8, 5 2 B. 2, 8, 3 2 C. 2, 8, 5 1 D. 2, 6, 7 2 Timberlake LecturePLUS 2000

19. Learning Check S3 Using the periodic table, write the complete electronic configuration for each: A. Cl B. Sr C. I Timberlake LecturePLUS 2000

20. Solution S3 Using the periodic table, write the complete electronic configuration for each: A. Cl 1s2 2s2 2p6 3s2 3p5 B. Sr 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 C. I 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5 Timberlake LecturePLUS 2000

21. Learning Check S4 A. The final two notations for Co are 1) 3p64s2 2) 4s24d7 3) 4s23d7 B. The final three notations for Sn are 1) 5s25p24d10 2) 5s24d105p2 3) 5s25d105p2 Timberlake LecturePLUS 2000

22. Solution S4 A. The final two notations for Co are 3) 4s2 3d7 B. The final three notations for Sn are 2) 5s2 4d10 5p2 Timberlake LecturePLUS 2000

23. Orbital • A 3 dimensional space around a nucleus in which electrons are most likely to be found • Shape represents electron density (not a path the electron follows) • Each orbital can hold up to 2 electrons. Timberlake LecturePLUS 2000

24. s orbitals 3s 2s 1s Timberlake LecturePLUS 2000

25. Three p Orbitals px pz py Timberlake LecturePLUS 2000

26. p subshell contains p orbitals Timberlake LecturePLUS 2000

27. d orbitals Timberlake LecturePLUS 2000

28. Learning Check S5 A. Number of electrons in a p orbital 1) 1e 2) 1e or 2e 3) 3e B. Number of orbitals in a p subshell 1) 1 2) 2 3) 3 C. Number of orbitals in 4d subshell 1) 1 2) 3 3) 5 D. Number of electrons (maximum) in a 3d subshell 1) 2e 2) 5e 3) 10e Timberlake LecturePLUS 2000

29. Solution S5 A. Number of electrons in a p orbital 2) 1e or 2e B. Number of orbitals in a p subshell 3) 3 C. Number of orbitals in 4d subshell 3) 5 D. Number of electrons in a 3d subshell 3) 10e Timberlake LecturePLUS 2000