Chemical Symbols, Formulas, and Compounds - Middle School Building ... - Free Printable

Let’s work through this step by step.

This worksheet is about building molecular models — like using a toy set where each atom has “holes” that must be connected to other atoms with “bonds” (represented by connectors). The key rule: ALL HOLES MUST BE FILLED. That means every atom must make exactly the number of bonds it’s supposed to, based on its chemistry.

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Step 1: Fill in the atom properties

We need to know how many holes (and thus bonds) each atom typically makes:

- Hydrogen (H) → always makes 1 bond → so it has 1 hole
- Oxygen (O) → usually makes 2 bonds → so it has 2 holes
- Nitrogen (N) → usually makes 3 bonds → so it has 3 holes
- Carbon (C) → always makes 4 bonds → so it has 4 holes
- Chlorine (Cl) → usually makes 1 bond → so it has 1 hole

So we fill in:

> Hydrogen ( H ) has 1 holes, and must make 1 bonds.
> Oxygen ( O ) has 2 holes, and must make 2 bonds.
> Nitrogen ( N ) has 3 holes, and must make 3 bonds.
> Carbon ( C ) has 4 holes, and must make 4 bonds.
> Chlorine ( Cl ) has 1 hole, and must make 1 bond.

*(Note: We use singular “hole” for chlorine since it’s 1, but the worksheet says “holes” generically — we’ll keep the wording as given.)*

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Step 2: Build structural diagrams for each molecule

Now we draw how the atoms connect so that ALL holes are filled.

We’ll go one by one:

#### 1. Hydrogen Gas (H₂)
- Two hydrogen atoms.
- Each needs 1 bond → they connect to each other.
- Diagram: H–H

#### 2. Oxygen Gas (O₂)
- Two oxygen atoms.
- Each needs 2 bonds → they must share 2 bonds (double bond).
- Diagram: O=O

#### 3. Nitrogen Gas (N₂)
- Two nitrogen atoms.
- Each needs 3 bonds → triple bond.
- Diagram: N≡N

#### 4. Methane (CH₄)
- One carbon (needs 4 bonds), four hydrogens (each needs 1 bond).
- Carbon in center, bonded to 4 H’s.
- Diagram:
```
H
|
H - C - H
|
H
```

#### 5. Water (H₂O)
- One oxygen (needs 2 bonds), two hydrogens (each needs 1 bond).
- Oxygen in center, bonded to 2 H’s.
- Diagram: H–O–H (bent shape, but for simple diagram, straight line is fine)

#### 6. Carbon Dioxide (CO₂)
- One carbon (needs 4 bonds), two oxygens (each needs 2 bonds).
- Carbon in center, double-bonded to each oxygen.
- Diagram: O=C=O

#### 7. Ethane (C₂H₆)
- Two carbons (each needs 4 bonds), six hydrogens.
- Carbons bonded together (single bond), then each carbon gets 3 hydrogens.
- Diagram:
```
H H
| |
H - C - C - H
| |
H H
```

#### 8. Ethylene (C₂H₄)
- Two carbons (each needs 4 bonds), four hydrogens.
- Carbons double-bonded to each other, each carbon gets 2 hydrogens.
- Diagram:
```
H H
\ /
C=C
/ \
H H
```
Or simpler: H₂C=CH₂

#### 9. Acetylene (C₂H₂)
- Two carbons (each needs 4 bonds), two hydrogens.
- Carbons triple-bonded, each carbon gets 1 hydrogen.
- Diagram: H–C≡C–H

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Final Check:

All atoms have their required number of bonds filled. No dangling holes. All molecules follow standard bonding rules.

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Final Answer:

Atom Properties:
- Hydrogen ( H ) has 1 holes, and must make 1 bonds.
- Oxygen ( O ) has 2 holes, and must make 2 bonds.
- Nitrogen ( N ) has 3 holes, and must make 3 bonds.
- Carbon ( C ) has 4 holes, and must make 4 bonds.
- Chlorine ( Cl ) has 1 holes, and must make 1 bonds.

Structural Diagrams:

| Molecule/Compound Name | Chemical Formula | STRUCTURAL DIAGRAM |
|------------------------|------------------|-----------------------------|
| Hydrogen Gas | H₂ | H–H |
| Oxygen Gas | O₂ | O=O |
| Nitrogen Gas | N₂ | N≡N |
| Methane | CH₄ | H<br> |<br>H–C–H<br> |<br> H |
| Water | H₂O | H–O–H |
| Carbon Dioxide | CO₂ | O=C=O |
| Ethane | C₂H₆ | H H<br> | |<br>H–C–C–H<br> | |<br>H H |
| Ethylene | C₂H₄ | H H<br> \ /<br> C=C<br> / \<br>H H |
| Acetylene | C₂H₂ | H–C≡C–H |

*(Note: In actual drawing, you’d sketch these neatly — above is text representation.)*