Question

name:
q3 chemistry: u5l3 vsepr theory day 2
date:
practice set 2

1. cs₂

lewis dot structure	compound name	# of electron groups	shape of molecule around central atom
			degree between terminal atoms

1. scl₂

lewis dot structure	compound name	# of electron groups	shape of molecule around central atom
			degree between terminal atoms

1. * ccl₄

lewis dot structure	compound name	# of electron groups	shape of molecule around central atom
			degree between terminal atoms

page 5

Explanation:

Problem 4: $\boldsymbol{CS_2}$

Step 1: Lewis Dot Structure

Carbon (C) has 4 valence electrons, sulfur (S) has 6. In $CS_2$, C is central. It forms double bonds with two S atoms:
$$\text{S}::\text{C}::\text{S}$$ (each S has 2 lone pairs, C has no lone pairs).

Step 2: Compound Name

Binary molecular compound: name first element (carbon), second (sulfur) with -ide suffix. So carbon disulfide.

Step 3: # of Electron Groups

Electron groups = bonding groups (no lone pairs on C). 2 double bonds → 2 electron groups.

Step 4: Molecular Shape

2 electron groups, no lone pairs → linear (VSEPR: $AX_2$).

Step 5: Bond Angle

Linear shape → bond angle = $180^\circ$.

Problem 5: $\boldsymbol{SCl_2}$

Step 1: Lewis Dot Structure

Sulfur (S) has 6 valence electrons, Cl has 7. S is central, bonded to 2 Cl atoms, with 2 lone pairs on S:
$$\text{Cl}-\text{S}-\text{Cl}$$ (each Cl has 3 lone pairs, S has 2 lone pairs).

Step 2: Compound Name

Binary molecular compound: sulfur dichloride.

Step 3: # of Electron Groups

Bonding groups (2) + lone pairs (2) → 4 electron groups.

Step 4: Molecular Shape

4 electron groups (2 bonding, 2 lone pairs) → bent (VSEPR: $AX_2E_2$).

Step 5: Bond Angle

Lone pairs repel, so angle < $109.5^\circ$ (approx $103^\circ$ for $SCl_2$).

Problem 6: $\boldsymbol{CCl_4}$

Step 1: Lewis Dot Structure

Carbon (C) has 4 valence electrons, Cl has 7. C is central, bonded to 4 Cl atoms (single bonds), no lone pairs on C:
$$\text{Cl}-\text{C}-\text{Cl}$$ (each Cl has 3 lone pairs, C has no lone pairs, 4 single bonds).

Step 2: Compound Name

Binary molecular compound: carbon tetrachloride.

Step 3: # of Electron Groups

4 single bonds → 4 electron groups (no lone pairs on C).

Step 4: Molecular Shape

4 electron groups, no lone pairs → tetrahedral (VSEPR: $AX_4$).

Step 5: Bond Angle

Tetrahedral shape → bond angle = $109.5^\circ$.

Answer:

s:

4. $CS_2$

• Lewis Dot Structure: $\boldsymbol{\text{S}::\text{C}::\text{S}}$ (S: 2 lone pairs each, C: 0)
• Compound Name: $\boldsymbol{\text{carbon disulfide}}$
• # of electron groups: $\boldsymbol{2}$
• Shape: $\boldsymbol{\text{linear}}$
• Bond angle: $\boldsymbol{180^\circ}$

5. $SCl_2$

• Lewis Dot Structure: $\boldsymbol{\text{Cl}-\text{S}-\text{Cl}}$ (Cl: 3 lone pairs each, S: 2 lone pairs)
• Compound Name: $\boldsymbol{\text{sulfur dichloride}}$
• # of electron groups: $\boldsymbol{4}$
• Shape: $\boldsymbol{\text{bent}}$
• Bond angle: $\boldsymbol{\approx 103^\circ}$ (or $< 109.5^\circ$)

6. $CCl_4$

• Lewis Dot Structure: $\boldsymbol{\text{Cl}-\text{C}-\text{Cl}}$ (4 single bonds, Cl: 3 lone pairs each, C: 0)
• Compound Name: $\boldsymbol{\text{carbon tetrachloride}}$
• # of electron groups: $\boldsymbol{4}$
• Shape: $\boldsymbol{\text{tetrahedral}}$
• Bond angle: $\boldsymbol{109.5^\circ}$