Electrons and Orbitals

1. Electrons and Orbitals

2. Quantum Mechanics Describes the arrangement of electrons in atoms in terms of: • Main or principal energy levels (n) • Orbitals(space occupied within the atom) • How many electrons in each orbital. • Basically, gives an address for every electron in an atom.

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…..

5. Orbitals • Orbitals exist within an energy level • All electrons in an orbital have the same energy • Designated s, p, d, f .. • energy: s<p<d<f

7. Electron Locations Main Energy Orbitals in Levels the energy level n=4 4s, 4p, 4d, 4f n=3 3s, 3p, 3d n=2 2s, 2p n=1 1s

8. S P D F

9. Electrons Allowed • All electrons in the same orbital have the same energy. • Within orbitals are sub-orbitals (part of an orbital….like apartments in a building). Each sub-orbital holds 2 electrons. s orbital 1 sub-orbital = 2electrons max. p orbital 3 sub-orbitals = 6 electrons max. d orbital 5 sub orbitals = 10electrons max. f orbital 7 sub-orbitals = 14electrons max.

10. S P D F

11. 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 Energy levelorbital Timberlake LecturePLUS 2000

12. S P D F

13. Writing Electron Configurations H He Li C S

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

15. Learning Check S2 Which if the following is the correct electron configuration for Chlorine? A. 1s22s22p63s1 B. 1s22s22p63s23p6 C. 1s22s22p63s23p5 D. 1s22p83s1 E. 1s22s22p63s23p7

16. Solution E2 C. 1s22s22p63s23p5

17. Learning Check S3 Using the periodic table, write the complete electronic configuration for each: A. Be B. F C. Mg Timberlake LecturePLUS 2000

18. Solution S3 Using the periodic table, write the complete electronic configuration for each: A. Be 1s22s2 B. F 1s2 2s2 2p5 C. Mg 1s2 2s2 2p63s2 Timberlake LecturePLUS 2000

19. 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 sub-orbital can hold up to 2 electrons.

20. s orbitals 3s 2s 1s

21. Three p Sub-Orbitals px pz py

22. p orbitals

23. d sub-orbitals

24. Review Questions A. Maximum number of electrons in p orbitals a) 2 b) 3 c) 6 B. Number of suborbitalsin a p orbital. a) 1 b) 2 c) 3 C. Maximum number of electrons in an S orbital a) 1 b) 2 c) 6

25. Solution A. Maximum number of electrons in p orbitals c) 6 B. Number of suborbitals in a p orbital. c) 3 C. Maximum number of electrons in an S orbital b) 2

26. Review Questions • 1) What scientist discovered the nucleus of the atom? • 2) Who said that electrons travel in ORBITS around the nucleus, like planets around the sun? • 3) Where in an atom will you find neutrons? Who discovered them?

27. Review Questions • 1) What scientist discovered the nucleus of the atom? Rutherford • 2) Who said that electrons travel in ORBITS around the nucleus, like planets around the sun? Bohr • 3) Where in an atom will you find neutrons? Who discovered them? • In the nucleus, tightly packed with the protons; Chadwick