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Electron Configuration

Electron Configuration. How electrons are arranged. Or Goodbye Bohr!. Quantum Mechanics. In quantum mechanics ,

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Electron Configuration

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  1. Electron Configuration How electrons are arranged Or Goodbye Bohr!

  2. Quantum Mechanics In quantum mechanics, the electrons occupy specific energy levels (as in Bohr's model) but they also exist within specific probability volumes called orbitals with specific orientations in space. The electrons within each orbital has a distinct spin.

  3. Probability Under this new model, we cannot predict exactly where an electron is. Rather we can say that electrons are most likely found within certain areas. These are called probability volumes (note the volume: 3D)

  4. 3s 2s 1s n = The principle quantum number Describes the possible energy levels (how close it is to the nucleus)and pictorially it describes the orbital size. n = 1, 2, 3….where an orbital with the value of 2 is larger than an orbital with the value of 1.

  5. Quantum Mechanics l = angular momentum quantum number Describes the "shape" of the orbital and can have values from 0 to n - 1 for each n. orbital designation : s p d f

  6. Quantum Mechanics ml= magnetic quantum number Related to the orientation of an orbital in space relative to the other orbitals with the same lquantum numbers. It can have values between l and - l. So for s, only 1 orientation is possible But for p, s orientations are possible How many are possible for d? f?

  7. Quantum Mechanics ms= spin quantum number An electron has either +1/2 or -1/2 spin values; sometimes referred to as spin up and spin down. These are arbitrary and are only used to designate different “addresses” for the electrons

  8. What does the electron cloud look like? NOT THIS!!!

  9. More like this: 1S 2Pz 2S 3S 2Px 2py Each orbital contains 2 electrons maximum, with opposite spins

  10. Electron Configuration Electron configuration is a shorthand notation for describing the arrangement of the electrons about the nucleus. General Format using the quantum numbers: n l e- RULES: 1. Fill the lowest energy levels first. 1s, 2s, 2p, 3s , 3p, 4s, 3d , 4p 2. No more than two electrons per orbital. 3. Ready for an easier way? n = principle quantum number l = angular momentum quantum number e- = number of electrons Lowest

  11. s p House Model d Least expensive rooms filled first d s p Two people per room s p d No one likes to share a room (only 1 bed) s p d People in the same bed sleep head to toe s p INKEEPERS RULES s

  12. PRICES 6s 6p 6p 6p 36 6d 6d 6d 6d House Model $$$ 5d 5d 5d 5d 5d 5s 5p 5p 5p $$ $ 4d 4d 4d 4d 4d 4s 4p 4p 4p 3s 3p 3p 3p 3d 3d 3d 3d 3d 2s 2p 2p 2p 1s

  13. 6s 6p 6p 6p 36 6d 6d 6d 6d House Model 5d 5d 5d 5d 5d 5s 5p 5p 5p 4d 4d 4d 4d 4d 4s 4p 4p 4p 3s 3p 3p 3p 3d 3d 3d 3d 3d 2s 2p 2p 2p 1s

  14. Electron Configuration Examples: H: 1s1 1s2 He: 1s2 2s1 Li : 1s2 2s2 2p6 3s2 3p6 4s2 3d7 Co: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 Br: red is valence electrons why aren’t d valence?

  15. The condensed electron configuration distinguishes the core electrons from the valence electrons. CORE electrons are tightly held to the nucleus and resemble a noble gas configuration. VALENCE electrons are the outer most electrons and are involved in chemical reactions. Examples of the condensed configuration: Li:[He] 2s1 Co:[Ar] 4s2 3d7 Br:[Ar] 4s2 3d10 4p5

  16. 10s 6g 6f 7f 5g 8d 7d 6d 5f 9p 8p 6p 7p 5d 4f 6s 9s 8s 7s 5p 4d 5s 4p 3d 4s 3p 3s 2p 2s 1s 10s 10p 10d 10f 10g 10h 9s 9p 9d 9f 9g 9h 8s 8p 8d 8f 8g 8h 7s 7p 7d 7f 7g 7h But check out this simple table at right. If you draw diagonal arrows starting at the bottom like this… 6s 6p 6d 6f 6g 6h 5s 5p 5d 5f 5g 4s 4p 4d 4f It shows the precise order in which the energy levels are arranged from lowest to highest! 3s 3p 3d 2s 2p 1s +

  17. So what does all this have to do with chemistry? Below is a rough sketch of the periodic table. For the sake of this discussion, we are going to move He over so it is in that little open space next to H: And now we are going to number the periods 1 through 7: As you will see, these periods correspond (more or less) to the energy levels we’ve just been discussing. s 1 2 p 1 He H 1 2 3 4 5 6 2 d 3 And we are going to designate the four distinct rectangular blocks by the type of sublevel they match up with: “s,” “p,” “d” and “f:” 1 2 3 4 5 6 7 8 9 10 4 5 6 7 And let’s also number the groups within each block (1,2,3,4…) f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Now let’s take the first ten sublevels (1s, 2s, 2p…) and see how the electrons filling these sublevels takes us row by row across the periodic table, and allows us to read electron configurations right off the table…

  18. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 OK, so we’re going to use arrows pointing up or down to represent the electrons. Can you guess into which box the first electron would go given that it is attracted to the nucleus? 1s +

  19. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s H f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s1 That’s right: it goes in the 1s sublevel. And its el. config is 1s2. Notice in the table above where H is – in the area designated as 1s. So where does the next electron go? 1s +

  20. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s He f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 If you were thinking it went in the 2s, then you forgot that each orbital can hold up to two electrons. Note how He is right here in the area designated as 1s2 and so its el. config. is 1s2. 1s +

  21. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s Li f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s1 Now that the 1s is filled, the next electron goes in the next sublevel – the 2s. Again note how Li is in 2s1. 1s Its full el. conf. is 1s2 2s1. What is Be’s el. conf? +

  22. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s Li f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s1 Now that the 1s is filled, the next electron goes in the next sublevel – the 2s. Again note how Li is in 2s1. 1s Its full el. conf. is 1s2 2s1. What is Be’s el. conf? +

  23. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s B f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 2p1 Is this what you were thinking? Notice how B is in the 2p1 spot. 1s So its full el. conf. is 1s2 2s2 2p1. What’s next? +

  24. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s C f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 2p2 Is this what you were thinking? Notice how C is in the 2p2 spot. So its el. conf. is 1s2 2s2 2p2 1s Notice also how when we fill a sublevel… +

  25. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s N f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 2p3 …we put one electron in each orbital until the sublevel is half filled… 1s +

  26. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s O f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 2p4 … and then we go back and start pairing off 1s This is called “Hund’s Rule, but it also referred to as the bus seat rule. Can you figure out why? +

  27. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s F f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 2p5 Look at F. It’s just one electron away from having filled 2p sublevel… 1s And it’s just one square away from the end of the 2p block. +

  28. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s Ne f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 2p6 And then Ne has a completely filled outer level. Na is next. Can you guess where the next electron is going to go? 1s +

  29. For example, Cl (#17) which is right here on the table: So the answer would be 1s2 2s2 2p6 3s2 3p5 The short cut would be: [Ne]3s2 3p5 1s2 1 2p6 3p5 2s2 2 3 3s2 4 5 6 7

  30. Orbital Diagrams Orbital diagrams are written in order of increasing energy levels starting with the lowest energy level the 1s orbital. ___ ___ ___ 4p ___ ___ ___ ___ ___ 3d ___ 4s ___ ___ ___ 3p ___ 3s ___ ___ ___ 2p ___ 2s ___ 1s RULES: (1) fill the lowest energy level first (2) fill each orbital in a subshell with one electron first before you double up. (3) Completely fill each subshell before proceeding to the next energy level. Remember the order!!

  31. Orbital DiagramsPractice Problems 1. Fill in the orbital diagrams for: C O Ne Na Si Cl Ar K ___ ___ ___ 4p ___ ___ ___ 4p __ __ __ __ __ 3d __ __ __ __ __ 3d ___ 4s ___ 4s ___ ___ ___ 3p ___ ___ ___ 3p ___ 3s ___ 3s ___ ___ ___ 2p ___ ___ ___ 2p ___ 2s ___ 2s ___ 1s ___ 1s

  32. Orbital DiagramsPractice Problem Answers Fill in the orbital diagrams for: C O ___ ___ ___ 4p ___ ___ ___ 4p __ __ __ __ __ 3d __ __ __ __ __ 3d ___ 4s ___ 4s ___ ___ ___ 3p ___ ___ ___ 3p ___ 3s ___ 3s ___ ___ ___ 2p ___ ___ ___ 2p ___ 2s ___ 2s ___ 1s ___ 1s

  33. Orbital DiagramsPractice Problem Answers Fill in the orbital diagrams for: Ne Na ___ ___ ___ 4p ___ ___ ___ 4p __ __ __ __ __ 3d __ __ __ __ __ 3d ___ 4s ___ 4s ___ ___ ___ 3p ___ ___ ___ 3p ___ 3s ___ 3s ___ ___ ___ 2p ___ ___ ___ 2p ___ 2s ___ 2s ___ 1s ___ 1s

  34. Orbital DiagramsPractice Problem Answers Fill in the orbital diagrams for: Si Cl ___ ___ ___ 4p ___ ___ ___ 4p __ __ __ __ __ 3d __ __ __ __ __ 3d ___ 4s ___ 4s ___ ___ ___ 3p ___ ___ ___ 3p ___ 3s ___ 3s ___ ___ ___ 2p ___ ___ ___ 2p ___ 2s ___ 2s ___ 1s ___ 1s

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