Chemistry

Week 13

Element quiz

Acid naming answers

Steps for drawing lewis structures

1. Atom farthest away from fluorine is center (hydrogen is never in center).
2. Total number of valence electrons.
3. Divide by 2 to find number of pairs.
4. Place bonds between atoms.
5. Place remaining pairs around atoms.
6. Is octet rule satisfied? May need to adjust for double and triple bonds.

* If it is a polyatomic ion, make sure to consider the charge when totaling the electrons.

Section 3, Question 39

39. Draw the Lewis structure for ethylene, C₂H₄.

Answer:

1. Furthest away from fluorine in middle, hydrogen always on outside.
2. Total valence: carbon: 4(x2), hydrogen: 1(x4). Total: 12
3. 12/2= 6 pairs
4. Start with single bonds between them all. 2 leftover.
5. Carbon has not satisfied octet, so add another bond.

Section 3, Question 41

41. Draw the Lewis structure for the NH₄⁺.

Answer:

1. Furthest away from fluorine in the middle, hydrogen always on outside.
2. Total valence: nitrogen: 5, hydrogen: 1(x4). Total: 9, but because of positive charge, take away one electron, so total=8.
3. 8/2= 4 pairs
4. Single bonds, bracket
5. Octet satisfied.

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Resonance structures

When more than one valid Lewis structure can be written.

Section 3, Question 43

43. Draw the Lewis resonance structure for NO₂^-.

Answer:

1. Furthest away from fluorine in middle.
2. Total valence: nitrogen: 5, oxygen: 6 (x2), total: 17 electrons. Due to negative charge, add one electron. Total: 18 electrons.
3. 18/2 = 9 pairs
4. Single bonds first, fill in leftover pairs as lone.
5. Nitrogen needs to satisfy octet. Double bond needed.

Section 3, Question 47

47. Draw the expanded octet Lewis structure for ClF₃

Answer:

1. Furthest from fluorine in middle.
2. Total valence: Cl: 7, F: 7 (x3), Total: 28
3. 28/2=14
4. Single bonds, then fill in lone pairs
5. Chlorine has 10 rather than 8

Section 3, Question 37

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37.Draw the Lewis structure for BH₃.

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1. Furthest away from fluorine in the middle, hydrogen always outside.
2. Total valence electrons Boron- 3, Hydrogen- 1 (x3), Total: 6
3. 6/2 = 3 pairs
4. No more available.
5. Boron is an exception to the rule of octet.

VSEPR Model: Valence Shell Electron Pair Repulsion

Section 4, QUESTION 56

56. Determine the molecular shape, bond angle, and hybrid orbitals for BF₃.

Answer: Find total pairs on central atom and shared pairs.

3, 3 therefore…

trigonal planar, 120 degrees, sp²

Section 4, Question 57

57. Determine the molecular shape, bon angle, and hybrid orbitals for OCl₂.

Answer: Find total pairs on central atom and shared pairs.

4, 2 therefore…

Bent, 104.5 degrees, sp³

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Section 4, Question 64

64. Compare the size of an orbital that has a shared electron pair with one that has a lone pair.

Answer: A lone pair occupies more space than a shared

Modeling!

Total Pairs:

Shared Pairs:

Lone Pairs:

Shape:

Intermolecular forces or van der waals forces

How strong?

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Strongest:

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Medium:

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Weakest:

Section 5, Question 75

75. Identify each molecules as polar or nonpolar: SCl₂, CS₂, and CF₄.

Answer:

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SCl₂ polar

CS₂ nonpolar

CF₄ nonpolar

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Station 4: gecko

https://www.youtube.com/watch?v=YeSuQm7KfaE

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https://www.youtube.com/watch?app=desktop&v=r5cqJTU5D5I

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gecko

Why can’t it walk on teflon?

Practice balancing a chemical equation

H₂ (g) + Cl₂ (g) → HCl (g)

homework

Tuesday: Read Chapter 9, Section 1 Questions 1, 4, 7, 11, 12

Wednesday: Read Chapter 9, Section 2 Questions 14, 18, 21, 25, 29, 30

Thursday: Read Chapter 9, Section 3, Questions 35, 40, 45, 46, 50-52

Friday: Study elements 46-60, be able to tell me the symbol if I give you the element.

links

https://www.youtube.com/watch?v=a7z43DI8Umw

https://www.youtube.com/watch?v=yA3TZJ2em6g

https://www.youtube.com/watch?v=aMU1RaRulSo

https://www.youtube.com/watch?v=2qX9MOQOmAM

https://www.youtube.com/watch?v=U9HyZLdCzZQ

https://www.youtube.com/watch?v=HKWrxVpKZWw

https://www.youtube.com/watch?v=z_uXWXmffSo

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