Published on

Published in: Technology, Education
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide


  1. 1. Picturing Molecules Amie Kuzara Boston College High School Chemistry I
  2. 2. HONC if you like Molecules Living By Chemistry Unit: Smells Investigation II – Lesson 2
  3. 3. What do you think? <ul><li>List three similarities and three differences for Molecule #1 and Molecule #2. </li></ul>
  4. 4. Key Terms <ul><li>Structural Formula is a drawing or diagram that a chemist uses to show how the atoms in a molecule are connected. </li></ul><ul><ul><li>The connections between atoms in a molecule are called bonds . </li></ul></ul><ul><ul><li>In a structural formula covalent bonds are represented with lines. </li></ul></ul>
  5. 5. What do you think? <ul><li>What patterns do you see in the bonding of hydrogen, oxygen, carbon, and nitrogen? </li></ul>
  6. 6. <ul><li>HONC </li></ul><ul><li>1 2 3 4 </li></ul>HONC!
  7. 7. Why HONC? 4 3 2 1 Covalent Bonds Formed 4 3 2 1 # e- needed to have full valence shell 4 5 6 1 Valence electrons C N O H  
  8. 8. Isomers <ul><li>Molecules are isomers of one another if they have the same molecular formula but different structural formulas. </li></ul>
  9. 9. Check-In <ul><li>Are these molecules correct according to the HONC rule? If not, what is wrong with them specifically? </li></ul>
  10. 10. Wrap-Up <ul><li>The HONC rule tells us how many times hydrogen, oxygen, nitrogen, and carbon tend to bond. </li></ul><ul><li>When a molecule is oriented differently in space it is still the same molecule. </li></ul><ul><li>A molecular formula can be associated with more than one distinct structural formula. </li></ul>
  11. 11. HONC Homework <ul><li>2. Sample answers for C 4 H 11 N: </li></ul>
  12. 12. HONC Homework <ul><li>3. Sample answers for C 4 H 10 : </li></ul>
  13. 13. HONC Homework <ul><li>3. Sample answers for C 5 H 12 O: </li></ul>
  14. 14. HONC Homework <ul><li>3. Sample answers for C 5 H 12 O: </li></ul>
  15. 15. Connect the Dots Living By Chemistry Unit: Smells Investigation II – Lesson 3
  16. 16. What do you think? <ul><li>The lines in this structural formula represent bonds. </li></ul><ul><li>What do you think a bond is? </li></ul>
  17. 17. Covalent Bonds <ul><li>A covalent bond is a connection that forms between two atoms when those atoms are share a pair of electrons between them. </li></ul>
  18. 18. Lewis Dot Structures
  19. 19. Lewis Dot Structures <ul><li>Each side of the side resembles an orbital </li></ul><ul><ul><li>1 s-orbital and 3 p-orbitals = 4 </li></ul></ul><ul><ul><li>Remember Hund’s Rule! </li></ul></ul><ul><ul><li>Deal out valence electrons like cards. </li></ul></ul>
  20. 20. HONC!
  21. 21. Connect the Dots
  22. 22. Connect the Dots
  23. 23. Connect the Dots II
  24. 24. Electron Pairs Lone Pair or Unshared Pair Bonding Pair or Shared Pair
  25. 25. Wrap-Up <ul><li>A covalent bond is one in which two atoms share valence electrons. </li></ul><ul><li>In a Lewis dot structure, pairs of electrons that are not bonded are referred to as lone pairs. </li></ul><ul><li>HONC indicates how many unpaired electrons are associated with hydrogen, oxygen, nitrogen, and carbon. </li></ul>
  26. 26. Eight is Enough Living By Chemistry Unit: Smells Investigation II – Lesson 4
  27. 27. What do you think? <ul><li>Draw the Lewis dot structure for the following covalently bonded molecule. Explain how you arrived at your answer. </li></ul><ul><li>Cl 2 </li></ul>
  28. 28. What do you think?
  29. 29. Eight is Enough
  30. 30. Eight is Enough #3
  31. 31. Eight is Enough #5&6
  32. 32. If you finish early…
  33. 33. The Octet Rule <ul><li>Atoms of most elements are very reactive . The become stable when they combine with other atoms to form compounds. </li></ul><ul><li>The octet rule states that atoms tend to form bonds by sharing valence electrons until eight valence electrons surround each atom. </li></ul><ul><ul><li>Example: oxygen tries to “become like” neon. </li></ul></ul><ul><ul><li>Exceptions: Hydrogen and Helium </li></ul></ul>
  34. 34. Check-In <ul><li>Which of the following formulas satisfy the HONC rule? </li></ul><ul><li>Which of the following formulas satisfy the octet rule? </li></ul><ul><li>Which of the following formulas represent stable compounds we might fight in the world around us? </li></ul><ul><li>a) CH 3 b) CH 4 </li></ul>
  35. 35. Wrap-Up <ul><li>Elements form bonds by sharing electrons. </li></ul><ul><li>Atoms form bonds until they have the same number of valence electrons as the noble gas in the same row of the periodic table </li></ul><ul><li>This is called the octet rule. </li></ul>
  36. 36. Dots, Dots, and More Dots Living By Chemistry Unit: Smells Investigation II – Lesson 5
  37. 37. What do you think? <ul><li>Here are the structural formulas for N 2 (nitrogen gas), O 2 (oxygen gas), F 2 (fluorine gas). </li></ul><ul><li>Draw the Lewis dot structures for these three molecules. </li></ul>
  38. 38. What do you think? Single Bond F 2 Double Bond O 2 Triple Bond N 2
  39. 39. Carbon Dioxide CO 2 <ul><li>Begin by drawing the Lewis dot symbols for the carbon and oxygen atoms: </li></ul>
  40. 40. Carbon Dioxide CO 2 <ul><li>Bring the atoms together: </li></ul><ul><li>The octet rule is NOT satisfied! </li></ul><ul><li>How can we satisfy the octet rule??? </li></ul>
  41. 41. Carbon Dioxide CO 2 <ul><li>Create double bonds : </li></ul><ul><li>Draw the structural formula </li></ul>
  42. 42. Lewis Dot Structure Strategies <ul><li>Identify the central atom of the molecule and work from there. (Usually one or more carbon atoms is central – not usually an oxygen atom and never a hydrogen.) </li></ul><ul><li>Determine the number of valence electrons for each atom and draw the Lewis dot symbols. </li></ul><ul><li>Begin to combine atoms with the central atom. </li></ul>
  43. 43. Lewis Dot Structure Strategies <ul><li>Check to see that all the atoms satisfy the octet rule. (Except for hydrogen atoms!) </li></ul><ul><li>Use HONC when you can to check your molecule. </li></ul><ul><li>Count the total number of valence electrons in your molecule. If should match the total number of valence electrons in the individual atoms. </li></ul>
  44. 45. Check-In <ul><li>We know two things about a certain molecule: </li></ul><ul><ul><li>The molecular formula is C 2 H 4 O 2 </li></ul></ul><ul><ul><li>The structure contains on C=O in it </li></ul></ul><ul><li>Using Lewis dot symbols and the octet rule to guide you, draw at least one possible structure for this molecule. </li></ul>
  45. 46. Check-In
  46. 47. Wrap-Up <ul><li>Atoms can form double and triple bonds to satisfy the octet rule. </li></ul>