Molecular Models of Covalent Compounds Worksheet | PDF - Free Printable

Let's solve this step-by-step for each molecule listed in the table. We'll complete the Electron Shell Diagram, Structural Formula, and Relation to Living Things for each compound.

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🔬 Understanding the Requirements:

- Electron Shell Diagram: Shows valence electrons around each atom, with shared pairs (bonds) shown between atoms.
- Structural Formula: Shows how atoms are connected using lines (single, double, or triple bonds).
- Relation to Living Things: Biological significance or role in living organisms.

We’ll use standard atomic valences:
- H: 1 valence electron
- Cl: 7 valence electrons
- O: 6 valence electrons
- S: 6 valence electrons
- N: 5 valence electrons (not used here)
- C: 4 valence electrons (not used here)

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✔ 1. H₂ – Hydrogen Gas

Already completed in the table.

- Electron Shell Diagram: Two hydrogen atoms sharing one pair of electrons (single bond). Each H has 2 electrons (duet rule).
- Structural Formula: H–H
- Relation to Living Things: Produced by some bacteria during fermentation or anaerobic metabolism.

✔ Already filled.

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✔ 2. HCl – Hydrochloric Acid

#### Electron Shell Diagram
- Hydrogen (H): 1 valence electron → shares 1 with Cl
- Chlorine (Cl): 7 valence electrons → needs 1 more to complete octet
- They form a single covalent bond.
- Diagram:
```
H : Cl
|
```
But properly drawn as:
- H with 2 electrons (shared pair), Cl with 8 electrons (6 lone pairs + 1 shared pair)

> Electron Shell Diagram:

#### Structural Formula
- H–Cl

#### Relation to Living Things
- Found in human stomach as gastric acid (HCl helps digest food and kill pathogens).
- Essential for protein digestion via activation of pepsin.

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✔ 3. Cl₂ – Chlorine Gas

#### Electron Shell Diagram
- Each chlorine has 7 valence electrons.
- Two Cl atoms share one pair → single covalent bond.
- Each Cl has 3 lone pairs (6 electrons) + 1 shared pair = 8 electrons (octet).

> Diagram:
```
:Cl : :Cl:
\
(bond)
```
Or better:
```
•• ••
:Cl—Cl:
•• ••
```

#### Structural Formula
- Cl–Cl

#### Relation to Living Things
- Toxic to most living organisms; used as a disinfectant in water treatment.
- Not naturally produced by living things but can be formed in trace amounts in biological systems under certain conditions (e.g., immune cells produce hypochlorous acid, HOCl, from Cl⁻).
- Used in swimming pools and sanitation.

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✔ 4. O₂ – Oxygen Gas

#### Electron Shell Diagram
- Each oxygen has 6 valence electrons.
- To achieve octet, they form a double bond.
- Double bond = two shared pairs.
- Each O has 2 lone pairs (4 electrons) + 2 shared pairs = 8 electrons.

> Diagram:
```
•• ••
:O=O:
•• ••
```

#### Structural Formula
- O=O

#### Relation to Living Things
- Essential for aerobic respiration in most living organisms.
- Used in cellular respiration to produce ATP.
- Inhaled by animals and humans, exhaled as CO₂ after use.

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✔ 5. H₂O – Water

#### Electron Shell Diagram
- Oxygen (O): 6 valence electrons → forms two single bonds with H.
- Each H contributes 1 electron → O shares 2 electrons (two single bonds).
- O has 2 lone pairs (4 electrons) + 2 bonds (4 electrons) = 8 electrons.
- Each H has 2 electrons (duet).

> Diagram:
```
••
H:O:H
••
```
Or better:
```
••
H—O—H
••
```
With two lone pairs on O.

#### Structural Formula
- H–O–H

#### Relation to Living Things
- The most important molecule for life.
- Solvent for biochemical reactions.
- Involved in hydration, temperature regulation, transport, and many metabolic processes.
- All known life forms require water.

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✔ 6. H₂S – Hydrogen Sulfide Gas

#### Electron Shell Diagram
- Sulfur (S): 6 valence electrons → forms two single bonds with H.
- Each H contributes 1 electron → S shares 2 electrons (two single bonds).
- S has 2 lone pairs (4 electrons) + 2 bonds = 8 electrons.
- Each H has 2 electrons.

> Diagram:
```
••
H:S:H
••
```
Or:
```
••
H—S—H
••
```

#### Structural Formula
- H–S–H

#### Relation to Living Things
- Produced by certain bacteria during anaerobic respiration (e.g., sulfate-reducing bacteria).
- Also produced in small amounts in human gut by microbes.
- Has a rotten egg smell; toxic at high concentrations.
- Can act as a signaling molecule in some physiological processes (e.g., vasodilation).

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✔ Final Completed Table:

| Molecule | What is it? | Electron Shell Diagram | Structural Formula | Relation to Living Things |
|---------|-------------|------------------------|--------------------|----------------------------|
| H₂ | Hydrogen Gas |  | H–H | Produced by some bacteria. |
| HCl | Hydrochloric Acid |  | H–Cl | Present in stomach acid; aids digestion. |
| Cl₂ | Chlorine Gas |  | Cl–Cl | Used in water purification; toxic to most organisms. |
| O₂ | Oxygen Gas |  | O=O | Essential for aerobic respiration. |
| H₂O | Water |  | H–O–H | Universal solvent; essential for all known life. |
| H₂S | Hydrogen Sulfide Gas |  | H–S–H | Produced by anaerobic bacteria; toxic but involved in signaling. |

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📌 Notes:

- Color codes (from instructions):
- Black = carbon
- Yellow = hydrogen
- Red = oxygen or sulfur
- Green = halogens (like Cl)
- Blue = nitrogen
- For molecular models:
- Single stick = single bond
- Springs = double/triple bonds (e.g., O₂ uses a double bond)

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