Chemistry Day 30. Tuesday, November 13 th Wednesday, November 14 th, 2018

Transcription

1 Chemistry Day 30 Tuesday, November 13 th Wednesday, November 14 th, 2018

2 Do-Now: Covalent Bonding CN B 1. Write down today s FLT 2. How can you tell if atoms will form an ionic or a covalent bond? 3. What are the two types of covalent bonds, and how do they differ? 4. Draw the electron dot diagram for Sulfur. 5. Use a pro-talk sentence frame to explain the concept of covalent bonding. 6. What do you need to do to prepare for the unit test after break? Take out your planner and ToC

3 FLT I will be able to describe the arrangement of electrons in covalent bonds using Lewis dot structures by completing Covalent Bonding CN B Standard HS-PS1-1: Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.

4 The Nature of Covalent Bonding

5 Recall

6 Recall Compounds are held together by chemical bonds Ionic Bond = electrostatic attraction due to the transfer of vse - s between a metal and nonmetal Covalent Bond = formed from the sharing of vse - s between nonmetals

7 Molecular vs. Ionic Compounds NaCl KBr CO 2 HBr NH 3 AlCl 3

8 Single, Double, Triple Bonds

9 Single, Double, Triple Bonds Covalent Bonds involve the sharing of valence electrons These electrons form strong single, double, or triple covalent bonds between the atoms

10 Single Bonds Single Bonds = Formed when atoms share one pair of vse - s (2 total) Drawn as a line between atoms Ex:

11 Single, Double, Triple However, sometimes atoms can share more than one pair of electrons. When this happens, double or triple bonds form.

12 Single, Double, Triple Double Bonds = atoms share two pairs of vse - s (4 total) Stronger and shorter than single bonds Noted as two lines

13 Single, Double, Triple Triple Bonds = atoms share three pairs of vse - s (6 total) Strongest, shortest, and most rigid Noted as three lines

14 Lewis Structures

15 Remind me How many valence electrons in 1. Li 2. S 3. Al 4. Br 5. Sr

16 Lewis Structures We can represent the covalent bonding patterns in atoms using Lewis structures

17 Rules for Drawing Lewis Structures 1. Determine the total number of valence e - s ex/ PBr 3

18 Rules for Drawing Lewis Structures 2. Place least EN atom in center and connect it to outer atoms with single bonds. Carbon is always in the center if present. Hydrogen is never in the center.

19 Rules for Drawing Lewis Structures 3. Use remainder of valence e - s to fill in octets around outer atoms* *Atoms in 1s or 2s, like H, can only have 2 e - s

20 Rules for Drawing Lewis Structures 4. Place extra valence e - s around the central atom

21 Rules for Drawing Lewis Structures 5. If you run out of valence e - s, use pairs to form double or triple bonds ex/ C 2 H 4

22 Things to Watch For: Never add extra e - s or bonds to H L

23 Things to Watch For: Add negative charges and subtract positive charges from the total valence e - s Ex/ NO 3 -

24 Things to Watch For: Indicate charges outside of brackets Ex/ NO 3 -

25 Things to Watch For: Resonance = If there are multiple possible structures, draw all with ßà in between Ex/ NO 3 -

26 Extra Notes There are always exceptions

27 Extra Notes Boron is a moron

28 Try This: SiBr 4 1. Find the total number valence electrons 2. Draw the Lewis structure 3. Compare with your neighbor

29 Molecular Geometry

30 The VSEPR Model VSEPR = Valence shell electron-pair repulsion This model is used to predict the geometries of molecules formed from nonmetals The molecular structure is the 3D arrangement of molecules in an atom The structure around a given atom is mostly determined by minimizing electron-pair repulsions Bonding and nonbonding e - pairs around an atom will be placed as far apart as possible

31 Video Notes

32 The VSEPR Model Types of Molecular Structures: Linear structure Molecule has a 180 o bond angle Ex/ BeCl 2

33 The VSEPR Model Types of Molecular Structures: Trigonal Planar Molecule has a planar (flat) and triangular structure with 120 o bond angles Ex/

34 The VSEPR Model Types of Molecular Structures: Tetrahedral Molecule has a bond angles of o. Occurs whenever four pairs of e- s are present around an atom. Ex/

35 The VSEPR Model Types of Molecular Structures: Trigonal Bipyramidal Ex/

36 The VSEPR Model Types of Molecular Structures: Octahedral: Ex/

37 To determine the shape: 1. Count number of electron regions around your central atom Any type of bond counts as one region, and a lone pair also counts as one region 2. Determine how many of those regions are lone pairs (memorize chart)

38 The VSEPR Model We can use the number of electron pairs to determine the probable molecular shape. Know these five:

39 The VSEPR Model We can use the number of electron pairs to determine the probable molecular shape. Know these five:

40 The VSEPR Model If there are no lone pairs, use the number of bonding regions to predict the shape 2 = linear 3 = trigonal planar 4 = tetrahedral 5 = trigonal bipyramidal 6 = octahedral

41 Try This: Draw the lewis structures, determine the molecular geometry, AND sketch the shape for the following: a. PCl 5

42 The VSEPR Model The presence of lone pairs count as electron regions; however, they will change the molecular geometry Ex/ H 2 O How many electron regions are around O?

43 The VSEPR Model Lone pairs require more room than bonded (shared) pairs, and tend to compress the angles between the bonding pairs

44 To sum up: The VSEPR Model Determine the TOTAL number of electron regions around the central atom Determine how many of those are lone pairs Generally, any resonance structure can be used to determine geometry

45 The VSEPR Model

46 The VSEPR Model

47 The VSEPR Model

48 The VSEPR Model

49 The VSEPR Model

50 The VSEPR Model

51 Try This: Draw the lewis structures, determine the molecular geometry, AND sketch the shape for the following: a. SO 2

52 The VSEPR Model Remember: this is just a model While it generally provides us with an accurate prediction, there are exceptions

53 Chemistry Day 31 Thursday, November 15 th Friday, November 16 th, 2018

54 Do-Now: Bonding Quiz Review Do-Now 1. Write down today s FLT 2. Distinguish between an ionic bond and a metallic bond. 3. Identify two properties of ionic compounds 4. Can calcium and phosphorous form an ionic bond? Why or why not? 5. Write down the formula for strontium nitride 6. What is meant by the term delocalized electrons? Take out your planner and ToC

55 Let s Kahoot J

56 Quiz Protocol You may have out: Pen and/or pencil Periodic Table Eyes on your own paper Noise Level 0 Check answers Flip over when finished