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Understanding Chemical Reactions & Electron Placement

Learn about electron configurations, quantum numbers, Lewis electron dot diagrams, and the principles that govern chemical reactions at the atomic level. Dive into electron placement theories with equations, models, and shortcuts.

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Understanding Chemical Reactions & Electron Placement

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  1. FACT: Chemical reactions happen because electrons are shared or transferred from one substance to another

  2. MAX NUMBER OF ELECTRONS IN AN ENERGY LEVEL

  3. Write a mathematical equation that allows us to predict the Max # if we know the energy level (n) Max # = …n…

  4. Equation to calculate Max # of e- 2n2 Where n is any energy level

  5. There are 4 Quantum #s and those #s are used to describe where an electron is likely to be found at any given time

  6. This is a lot like being able to use four “places” to describe EXACTLY where Mr. T should be at 8:00AM on Friday.

  7. The Principle Quantum # The first number we already know… (a.k.a. The NRG level)

  8. 1st Quantum # Specifies the energy level that the electron is on Principle Quantum #

  9. Principle Quantum # (IDEA Academy’s Street)

  10. 2nd Quantum # Specifies the shape of the sub-energy level

  11. s and p Sub Energy Levels

  12. III. Quantum Mechanical Model: Atomic Orbitals E. Shapes of orbitals d orbitals

  13. ORBITAL Space occupied by a pair of electrons

  14. Four Sub-Energy Levels

  15. Sub-Energy Levels

  16. So why do electrons fill in like they do? i.e. why is K’s last electron in the 4th NRG level?

  17. 2 Factors Influencing Electron Placement • Energy Level • - Closer to nucleus=easy 2. Subenergy level (shape) - spdf

  18. Electron Configuration A detailed way of showing the order in which electrons fill in around the nucleus

  19. # of e- in sub-energy level Electron Configuration Symbols 5f3 Sub-Energy Level Energy Level

  20. Electron Configuration PT

  21. Bohr Models vs. e- Configs K K: 1s2 3s2 3p6 4s1 2p6 2s2

  22. 1s1 Write the e-config for: He: 1s2 Li: 1s22s1 H: K: 1s22s22p63s23p64s1

  23. Valence Electrons Electrons in the outermost energy level (involved in chemical reactions)

  24. K: 1s22s22p63s23p64s1 Noble Gas Shortcut K: [Ar] 4s1

  25. Aufbau Principle All lower energy sublevels must be full before high energy sublevels begin filling in

  26. Steps for writing NGSC Write the noble gas preceding the desired element [in brackets] Carry on as usual

  27. With only the first two Quantum #s, do we have as much information as possible as to where the electrons are likely to be found?

  28. 3rd Quantum # Specifies the orientation of an orbital in space m or magnetic Q#

  29. 4th Quantum # Spin of an electron on its own axis s or spin Q#

  30. Quantum Review 1st Q#: Energy Level 2nd Q#: Shape of sub 3rd Q#: Orientation of Orbital 4th Q#: Spin of e-

  31. Quantum Review Principle (n): 1, 2, 3, 4, … Azimuthal (l): 0, 1, 2, 3 Magnetic (ml): …-2, -1, 0, 1, 2 Spin (ms): +1/2 or -1/2

  32. Pauli Exclusion Principle No 2 electrons can have the same set of 4 quantum numbers

  33. Arrow-Orbital Diagrams A way to show orbital filling, spin, relative energy

  34. Hund’s Rule Most stable arrangement of electrons is the one with the maximum number of unpaired electrons

  35. Arrow-Orbital Diagrams Energy 3d 4s 3p 3s 2p 2s 1s

  36. Lewis Electron Dot Diagrams The easiest way to represent the # of valance electrons

  37. Steps for writing electron dot diagrams Write the element’s symbol Write out e- config Count # of valence e-s (1-8) Place same # of dots as e- around symbol

  38. Order to fill in an e-dot 3 6 Bm 4 1 7 2 5 8

  39. What up? Bm 1 Who do 1 and 2 represent? 2 Why do 1 and 2 fill in on the same side?

  40. What up? 3 6 Bm 4 Who do 3-8 represent? 7 5 8 Why do 3,4,5 and 6,7,8 fill in on different sides?

  41. What up? 3 6 Bm 4 1 7 2 5 8 Why will you never have more than eight dots?

  42. Examples of Lewis Electron Dots

  43. What is different between the dot diagrams below and the ones that we’ve been doing? Our way accounts for Quantum #s, this way doesn’t!

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