2. Electron Configuration Normal configuration Orbital notation

3. Outside the nucleus: Outside the nucleus: SSSShell or energy level – main area where the electrons are found SSSSublevel or Subshell – subdivision of the main shell OOOOrbital – a three-dimensional space where the electron is found with greatest probability.

4. Main Energy Levels

5. The main energy levels are identified by numbers (1,2,3…7) or by letters (K,L,M…). The first main energy level has the lowest energy and is filled up with electrons first.

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7. Sublevels  These are represented by letters (s,p,d,f)  The first main energy level can only have up to 1 sublevel (1s). The second main energy level can have up to 2 sublevels (2s and 2p). The third sublevel can have 3 sublevels (3s,3p, and3d)  Each sublevel has a specific maximum number of electrons that it can hold  The s sublevel can only hold up to two electrons, the p can hold up to six, the d can hold up to ten and the f sublevel can hold up to fourteen electrons.

8. The main energy levels can be viewed as being divided into sublevels as in this diagram: Sublevels are filled according to increasing energy (not in regular order) because some over lapping occurs. Question: List the sublevels order from the lowest to the highest from the lowest to the highest energy. energy.

9. Diagonal Rule Follow the tail of the first arrow to its tip  Follow the tail of the first arrow to its tip  then go to the next arrow to the ne arrow   SEQUENCE:   1s, 2s, 2p 3s 3p, 4s3d 4s, 3d, 4p, 5s,4d,

10. Electron Configuration Notation  This method designates the energy level, the sublevel, and the number of electrons in each sublevel. For example Fluorine (9 electrons) 2 25 (2+2+5) 1 s 2 2 s 2 2 p 5 (2+2+5)

11. Electron Configuration of Some Elements  H (1 electron) H = 1s 1  He(2 electrons) He = 1s 2  Li (3 electrons) Li = 1s 2 2s 1  C (6 electrons) C = 1s 2 2s 2 2p 2

12. Electron Configuration of Some Elements  F (9 electrons) F = 1s 2 2s 2 2p 5  Al (13 electrons) Al = 1s 2 2s 2 2p 6 3s 2 3p 1  Ar ( 18 electrons) Ar = 1s 2 2s 2 2p 6 3s 2 3p 6  Fe = (26 electrons) Fe+ 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6

13. Electron Filling in Periodic Table 1 2 3 4 5 6 7 s d p s f    

14. Order of Filling Orbitals 1s1s 2s2s 3s3s 4s4s 5s5s 6s6s 7s7s 3d3d 4d4d 5d5d 6d6d 2p2p 3p3p 4p4p 5p5p 6p6p 1s1s La Ac 1 3 4 5 6 7 4f4f 5f5f Lanthanide series Actinide series Groups 8 Periods 1 2 2 3 4 5 6 7 Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 345

15. ORBITAL NOTATION  Another way to represent electron arrangement in an atom is thru orbital diagrams  Orbitals are 3-dimensional regions in space which have the highest probabilities of containing an electron  Orbitals can have a maximum of two electrons only

16. SublevelMax. No. of Electrons Max. No. of Orbitals Orbital Diagram s 2 1 p 6 3 d 10 5 f 14 7 Orbital Notation of different sublevels

17. In orbital notations, electrons are represented by half-arrows placed inside boxes that represent orbitals