Chemistry worksheet on molecular shape and polarity with compounds and questions for analysis.

Let's solve each compound step by step for Lewis structure, molecular shape, polarity of bonds, whether polar bonds cancel out, and finally, whether the molecule is polar.

---

1. CH₄ (Methane)

- Lewis Structure:
Carbon (C) has 4 valence electrons; each H has 1.
C bonded to 4 H atoms with single bonds. No lone pairs on C.
```
H
|
H--C--H
|
H
```

- Molecular Shape: Tetrahedral (4 bonding pairs, 0 lone pairs)

- Polar Covalent Bonds?
C–H bonds are slightly polar, but very weakly due to small electronegativity difference (~0.4). Often considered nonpolar covalent.

- Do Polar Bonds Cancel Out?
Yes — symmetrical tetrahedral shape → bond dipoles cancel.

- Is the Molecule Polar?
No — nonpolar molecule.

---

2. H₂O (Water)

- Lewis Structure:
Oxygen has 6 valence electrons; each H has 1.
O bonded to 2 H atoms, with 2 lone pairs on O.
```
H
|
.. ..
O
|
H
```

- Molecular Shape: Bent (or angular) — 2 bonding pairs, 2 lone pairs → electron geometry: tetrahedral

- Polar Covalent Bonds?
Yes — O–H bonds are highly polar (ΔEN ≈ 1.4)

- Do Polar Bonds Cancel Out?
No — bent shape causes unequal distribution of charge.

- Is the Molecule Polar?
Yes — polar molecule.

---

3. NH₃ (Ammonia)

- Lewis Structure:
Nitrogen has 5 valence electrons; each H has 1.
N bonded to 3 H atoms, with 1 lone pair on N.
```
H
|
.. ..
N
|
H
|
H
```

- Molecular Shape: Trigonal pyramidal (3 bonding pairs, 1 lone pair)

- Polar Covalent Bonds?
Yes — N–H bonds are polar (ΔEN ≈ 0.9)

- Do Polar Bonds Cancel Out?
No — asymmetrical shape leads to net dipole.

- Is the Molecule Polar?
Yes

---

4. CH₃OH (Methanol)

- Lewis Structure:
Carbon bonded to 3 H and 1 O; O bonded to C and H. O has 2 lone pairs.
```
H
|
H--C--O--H
|
H
```
(O has two lone pairs)

- Molecular Shape:
- Around C: Tetrahedral (4 single bonds)
- Around O: Bent (like water, 2 bonds + 2 lone pairs)

- Polar Covalent Bonds?
Yes — C–O and O–H bonds are polar (O is more electronegative)

- Do Polar Bonds Cancel Out?
No — asymmetric structure and presence of O–H bond → net dipole

- Is the Molecule Polar?
Yes

---

5. O₂ (Oxygen gas)

- Lewis Structure:
Double bond between two O atoms. Each O has 2 lone pairs.
```
:O=O:
```

- Molecular Shape: Linear (diatomic)

- Polar Covalent Bonds?
No — same atoms → identical electronegativity → nonpolar covalent bond

- Do Polar Bonds Cancel Out?
Not applicable — no polarity in the bond

- Is the Molecule Polar?
No — nonpolar molecule

---

6. N₂ (Nitrogen gas)

- Lewis Structure:
Triple bond between two N atoms. Each N has one lone pair.
```
:N≡N:
```

- Molecular Shape: Linear

- Polar Covalent Bonds?
No — identical atoms → nonpolar covalent bond

- Do Polar Bonds Cancel Out?
Not applicable — no polarity

- Is the Molecule Polar?
No

---

7. OF₂ (Oxygen difluoride)

- Lewis Structure:
O central atom bonded to 2 F atoms. O has 2 lone pairs.
Fluorine atoms have 3 lone pairs each.
```
F
|
.. ..
O
|
F
```

- Molecular Shape: Bent (similar to water) — 2 bonding pairs, 2 lone pairs on O

- Polar Covalent Bonds?
Yes — O–F bonds are polar (F is more electronegative than O)

- Do Polar Bonds Cancel Out?
No — bent shape → dipoles do not cancel

- Is the Molecule Polar?
Yes

> Note: Even though O is more electronegative than many elements, F is *more* electronegative than O (F = 4.0, O = 3.5), so O–F bonds are polar with dipole pointing toward F.

---

8. BF₃ (Boron trifluoride)

- Lewis Structure:
B has 3 valence electrons; each F has 7.
B bonded to 3 F atoms with single bonds.
B has no lone pairs, F atoms each have 3 lone pairs.
```
F
|
F--B--F
```

- Molecular Shape: Trigonal planar (3 bonding pairs, 0 lone pairs)

- Polar Covalent Bonds?
Yes — B–F bonds are polar (F is much more electronegative)

- Do Polar Bonds Cancel Out?
Yes — symmetrical trigonal planar shape → dipoles cancel

- Is the Molecule Polar?
No — nonpolar molecule despite polar bonds

---

✔ Final Answers Table:

| Compound | Lewis Structure | Sketch the Shape | Are there Polar Covalent Bonds? | Do Polar Bonds Cancel Out? | Is the Molecule Polar? |
|--------|------------------|-------------------|-------------------------------|----------------------------|-------------------------|
| 1. CH₄ | C bonded to 4 H (no lone pairs) | Tetrahedral | No (or very weak) | Yes | No |
| 2. H₂O | O bonded to 2 H, 2 lone pairs | Bent | Yes | No | Yes |
| 3. NH₃ | N bonded to 3 H, 1 lone pair | Trigonal pyramidal | Yes | No | Yes |
| 4. CH₃OH | C–O–H, O has 2 lone pairs | Asymmetric (tetrahedral C, bent O) | Yes | No | Yes |
| 5. O₂ | :O=O: | Linear | No | N/A | No |
| 6. N₂ | :N≡N: | Linear | No | N/A | No |
| 7. OF₂ | O bonded to 2 F, 2 lone pairs | Bent | Yes | No | Yes |
| 8. BF₃ | B bonded to 3 F (no lone pairs) | Trigonal planar | Yes | Yes | No |

---

📌 Summary Notes:

- Polarity depends on both bond polarity AND molecular geometry.
- Symmetrical molecules with polar bonds can be nonpolar if dipoles cancel.
- Asymmetrical molecules or those with lone pairs often result in net dipole moments → polar molecules.
- Diatomic molecules with same atoms (O₂, N₂) are always nonpolar.

Let me know if you'd like a visual sketch or diagram version!