Worksheet for predicting molecular shapes using Lewis structures and VSEPR theory.

Let’s go step by step to fill in the table for each molecule. We’ll use basic rules of chemistry that you’ve probably learned:

1. Lewis structure – shows how atoms are bonded and where lone pairs are.
2. Molecular shape (VSEPR) – based on electron domains around central atom.
3. Bond angle – depends on shape (e.g., tetrahedral = 109.5°, trigonal planar = 120°, etc.)
4. Polarity – if bonds are polar AND shape doesn’t cancel them out → molecule is polar.

We’ll do one row at a time.

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Row 1: CH₄ (already done as example)

- Lewis: C with 4 H’s, no lone pairs
- Shape: Tetrahedral
- Bond angle: 109.5°
- Polar? No — symmetric, all bonds same → nonpolar

✔ Already correct.

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Row 2: BeF₂

Step 1: Lewis Structure
- Beryllium (Be) has 2 valence electrons.
- Each F has 7, needs 1 more → forms single bond with Be.
- So: F–Be–F
- Be has only 2 bonds, no lone pairs → total electron domains = 2

Step 2: Molecular Shape
- 2 bonding domains, 0 lone pairs → Linear

Step 3: Bond Angle
- Linear → 180°

Step 4: Polarity
- Be-F bonds are polar (F is very electronegative), but because it’s linear and symmetric, dipoles cancel → Nonpolar

✔ Fill in:
- A: F–Be–F (with two dots on each F for lone pairs — but since we’re writing simply, just show bonds)
- B: Linear
- C: 180°
- D: Nonpolar

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Row 3: PCl₃

Step 1: Lewis Structure
- Phosphorus (P) has 5 valence electrons.
- Each Cl has 7, needs 1 → forms single bond with P.
- So P bonded to 3 Cl atoms → uses 3 electrons → 2 left → 1 lone pair on P.
- Total electron domains: 3 bonds + 1 lone pair = 4

Step 2: Molecular Shape
- Electron geometry: tetrahedral (4 domains)
- But one is lone pair → molecular shape = Trigonal Pyramidal

Step 3: Bond Angle
- Less than 109.5° because lone pair pushes bonds closer → about 107° (we can write “<109.5°” or “~107°”)

Step 4: Polarity
- P-Cl bonds are polar, and shape is not symmetric (pyramid) → dipoles don’t cancel → Polar

✔ Fill in:
- A: P with 3 Cl’s and one lone pair (drawn as :PCl₃ or describe)
- B: Trigonal Pyramidal
- C: ~107° (or <109.5°)
- D: Polar

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Row 4: CO₂

Step 1: Lewis Structure
- Carbon has 4 valence electrons.
- Oxygen has 6, needs 2 → so double bonds!
- O=C=O
- No lone pairs on C, each O has 2 lone pairs.
- Electron domains on C: 2 double bonds → count as 2 domains

Step 2: Molecular Shape
- 2 bonding domains, 0 lone pairs → Linear

Step 3: Bond Angle
- 180°

Step 4: Polarity
- C=O bonds are polar, but linear and symmetric → dipoles cancel → Nonpolar

✔ Fill in:
- A: O=C=O (each O with two lone pairs)
- B: Linear
- C: 180°
- D: Nonpolar

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Row 5: PF₅

Step 1: Lewis Structure
- Phosphorus (P) has 5 valence electrons.
- Each F needs 1 → forms 5 single bonds.
- P has 5 bonds, no lone pairs → 5 electron domains

Step 2: Molecular Shape
- 5 bonding domains → Trigonal Bipyramidal

Step 3: Bond Angles
- In trigonal bipyramidal: equatorial angles = 120°, axial-equatorial = 90°
- Usually we say “90° and 120°”

Step 4: Polarity
- All P-F bonds are polar, but shape is symmetric → dipoles cancel → Nonpolar

✔ Fill in:
- A: P with 5 F’s (three in plane, one up, one down)
- B: Trigonal Bipyramidal
- C: 90° and 120°
- D: Nonpolar

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Row 6: SO₂

Step 1: Lewis Structure
- Sulfur (S) has 6 valence electrons.
- Each O needs 2 → but S can form double bonds.
- One common structure: S double bonded to one O, single bonded to other O (which has negative charge), and S has positive charge → resonance.
- Or simpler: S with one double bond, one single bond, and one lone pair → total 3 electron domains.

Actually, best way:
- S central, bonded to two O’s.
- One double bond, one single bond (with formal charges), and one lone pair on S → total 3 electron domains.

Step 2: Molecular Shape
- 3 electron domains: 2 bonding, 1 lone pair → Bent (or V-shaped)

Step 3: Bond Angle
- Less than 120° because lone pair pushes → about 119° (we can say “<120°”)

Step 4: Polarity
- Bonds are polar, shape is bent → dipoles don’t cancel → Polar

✔ Fill in:
- A: S with one double bond to O, one single bond to O (and lone pair on S)
- B: Bent
- C: ~119° (or <120°)
- D: Polar

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Now let’s answer question Q3 at bottom:

> Q3: What does "VSEPR" stand for? Is the molecular shape the same as associated with their shapes, what is the minimum number of atoms a molecule must have? Explain.

Wait — the question seems cut off. Let me read again:

> “What does 'VSEPR' stand for? Is the molecular shape the same as associated with their shapes, what is the minimum number of atoms a molecule must have? Explain.”

That middle part is confusing. Probably meant:

> “What does ‘VSEPR’ stand for? Is the molecular shape always the same as the electron domain geometry? What is the minimum number of atoms a molecule must have? Explain.”

But since it says “Is the molecular shape the same as associated with their shapes” — maybe typo.

Let’s assume standard questions:

1. VSEPR stands for: Valence Shell Electron Pair Repulsion

2. Is molecular shape same as electron domain geometry? → No, because lone pairs affect shape but aren’t part of molecular shape. Example: NH₃ has tetrahedral electron geometry but trigonal pyramidal molecular shape.

3. Minimum number of atoms in a molecule? → 2 (like O₂, N₂, HCl). A molecule must have at least two atoms bonded together. Single atoms (like He) are not molecules.

So answer:

VSEPR = Valence Shell Electron Pair Repulsion
Molecular shape ≠ electron domain geometry when there are lone pairs.
Minimum atoms in a molecule = 2

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Final Answer:

Here’s the completed table:

| # | Molecule | A. Lewis Structure | B. Molecular Shape | C. Bond Angle | D. Polar/Nonpolar |
|---|----------|-----------------------------|----------------------------|---------------------|-------------------|
| 1 | CH₄ | H-C-H (tetrahedral) | Tetrahedral | 109.5° | Nonpolar |
| 2 | BeF₂ | F-Be-F | Linear | 180° | Nonpolar |
| 3 | PCl₃ | P with 3 Cl and 1 lone pair | Trigonal Pyramidal | ~107° | Polar |
| 4 | CO₂ | O=C=O | Linear | 180° | Nonpolar |
| 5 | PF₅ | P with 5 F | Trigonal Bipyramidal | 90° and 120° | Nonpolar |
| 6 | SO₂ | S with 2 O (one double, one single, lone pair) | Bent | ~119° | Polar |

Q3 Answer:
- VSEPR stands for Valence Shell Electron Pair Repulsion.
- Molecular shape is NOT always the same as electron domain geometry — lone pairs change the shape.
- Minimum number of atoms in a molecule is 2 (e.g., O₂).