Question

i) vsepr. draw the lewis structure for each of the following and determine the vsepr geometry. draw any resonance structures that apply. (5 pts each)

1. cbr₄
2. h₂s
3. hcn
4. sf₆
5. sio₂
6. so₃

Explanation:

Step1: Calculate total valence electrons for $\text{CBr}_4$

C: 4 valence e⁻, 4 Br: $4 \times 7 = 28$ e⁻. Total: $4 + 28 = 32$ e⁻

Step2: Draw $\text{CBr}_4$ Lewis structure

Central C bonded to 4 Br atoms (4 single bonds = 8 e⁻). Each Br has 3 lone pairs ($4 \times 6 = 24$ e⁻). Total e⁻ used: $8 + 24 = 32$ e⁻. No resonance.

Step3: Determine $\text{CBr}_4$ VSEPR geometry

4 bonding pairs, 0 lone pairs on central C: electron domain = 4. Geometry: Tetrahedral
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Step1: Calculate total valence electrons for $\text{H}_2\text{S}$

S: 6 valence e⁻, 2 H: $2 \times 1 = 2$ e⁻. Total: $6 + 2 = 8$ e⁻

Step2: Draw $\text{H}_2\text{S}$ Lewis structure

Central S bonded to 2 H atoms (2 single bonds = 4 e⁻). S has 2 lone pairs (4 e⁻). Total e⁻ used: $4 + 4 = 8$ e⁻. No resonance.

Step3: Determine $\text{H}_2\text{S}$ VSEPR geometry

2 bonding pairs, 2 lone pairs on central S: electron domain = 4. Geometry: Bent (V-shaped)
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Step1: Calculate total valence electrons for $\text{HCN}$

H:1, C:4, N:5 valence e⁻. Total: $1 + 4 + 5 = 10$ e⁻

Step2: Draw $\text{HCN}$ Lewis structure

H bonded to C (single bond = 2 e⁻), C triple-bonded to N (6 e⁻). N has 1 lone pair (2 e⁻). Total e⁻ used: $2 + 6 + 2 = 10$ e⁻. No resonance.

Step3: Determine $\text{HCN}$ VSEPR geometry

2 bonding pairs, 0 lone pairs on central C: electron domain = 2. Geometry: Linear
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Step1: Calculate total valence electrons for $\text{SF}_6$

S:6 valence e⁻, 6 F: $6 \times 7 = 42$ e⁻. Total: $6 + 42 = 48$ e⁻

Step2: Draw $\text{SF}_6$ Lewis structure

Central S bonded to 6 F atoms (6 single bonds = 12 e⁻). Each F has 3 lone pairs ($6 \times 6 = 36$ e⁻). Total e⁻ used: $12 + 36 = 48$ e⁻. No resonance.

Step3: Determine $\text{SF}_6$ VSEPR geometry

6 bonding pairs, 0 lone pairs on central S: electron domain = 6. Geometry: Octahedral
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Step1: Calculate total valence electrons for $\text{SiO}_2$

Si:4 valence e⁻, 2 O: $2 \times 6 = 12$ e⁻. Total: $4 + 12 = 16$ e⁻

Step2: Draw $\text{SiO}_2$ Lewis structure

Central Si double-bonded to 2 O atoms (2 double bonds = 8 e⁻). Each O has 2 lone pairs ($2 \times 4 = 8$ e⁻). Total e⁻ used: $8 + 8 = 16$ e⁻. No resonance.

Step3: Determine $\text{SiO}_2$ VSEPR geometry

2 bonding pairs, 0 lone pairs on central Si: electron domain = 2. Geometry: Linear
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Step1: Calculate total valence electrons for $\text{SO}_3$

S:6 valence e⁻, 3 O: $3 \times 6 = 18$ e⁻. Total: $6 + 18 = 24$ e⁻

Step2: Draw $\text{SO}_3$ Lewis structures

Central S bonded to 3 O atoms. Resonance structures: 1 double bond and 2 single bonds, with the double bond alternating between each O. Each structure uses 24 e⁻ (3 bonds = 6-8 e⁻, lone pairs on O = 16-18 e⁻). 3 resonance forms total.

Step3: Determine $\text{SO}_3$ VSEPR geometry

3 bonding pairs, 0 lone pairs on central S: electron domain = 3. Geometry: Trigonal Planar

Answer:

1. $\text{CBr}_4$:

Lewis structure: Central C with 4 single bonds to Br; each Br has 3 lone pairs. No resonance.
VSEPR Geometry: Tetrahedral

1. $\text{H}_2\text{S}$:

Lewis structure: Central S with 2 single bonds to H, 2 lone pairs on S. No resonance.
VSEPR Geometry: Bent (V-shaped)

1. $\text{HCN}$:

Lewis structure: $\text{H}-\text{C} \equiv \text{N}$; N has 1 lone pair. No resonance.
VSEPR Geometry: Linear

1. $\text{SF}_6$:

Lewis structure: Central S with 6 single bonds to F; each F has 3 lone pairs. No resonance.
VSEPR Geometry: Octahedral

1. $\text{SiO}_2$:

Lewis structure: $\text{O}=\text{Si}=\text{O}$; each O has 2 lone pairs. No resonance.
VSEPR Geometry: Linear

1. $\text{SO}_3$:

Lewis structure: 3 resonance forms, each with central S bonded to 3 O (1 double bond, 2 single bonds, alternating double bond position).
VSEPR Geometry: Trigonal Planar