Worksheet starter|KS3 Chemistry - Free Printable

Let's solve the task step by step.

We are given a table with the name of substance, a diagram of the molecule, and we need to fill in the chemical formula and determine whether it is an element or compound.

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🔍 Definitions:

- Element: A substance made of only one type of atom.
- Compound: A substance made of two or more different types of atoms chemically bonded together.

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Now, let’s go through each row:

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1. Water

- Diagram: One red oxygen (O) atom bonded to two white hydrogen (H) atoms.
- Chemical formula: H₂O
- Element or compound?: Compound (two different elements: H and O)

✔ Answer:
- Chemical formula: H₂O
- Element or compound: Compound

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2. Nitrogen

- Diagram: Two blue nitrogen (N) atoms bonded together.
- Chemical formula: N₂
- Element or compound?: Element (only nitrogen atoms)

✔ Answer:
- Chemical formula: N₂
- Element or compound: Element

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3. Carbon dioxide

- Diagram: One black carbon (C) atom bonded to two red oxygen (O) atoms.
- Chemical formula: CO₂
- Element or compound?: Compound (C and O)

✔ Answer:
- Chemical formula: CO₂
- Element or compound: Compound

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4. Ammonia

- Diagram: One blue nitrogen (N) atom bonded to three white hydrogen (H) atoms.
- Chemical formula: NH₃
- Element or compound?: Compound (N and H)

✔ Answer:
- Chemical formula: NH₃
- Element or compound: Compound

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5. Sulfur dioxide

- Diagram: One yellow sulfur (S) atom bonded to two red oxygen (O) atoms.
- Chemical formula: SO₂
- Element or compound?: Compound (S and O)

✔ Answer:
- Chemical formula: SO₂
- Element or compound: Compound

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6. Hydrogen

- Diagram: Two white hydrogen (H) atoms bonded together.
- Chemical formula: H₂
- Element or compound?: Element (only hydrogen atoms)

✔ Answer:
- Chemical formula: H₂
- Element or compound: Element

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7. Hydrogen chloride

- Diagram: One green chlorine (Cl) atom bonded to one white hydrogen (H) atom.
- Chemical formula: HCl
- Element or compound?: Compound (H and Cl)

✔ Answer:
- Chemical formula: HCl
- Element or compound: Compound

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8. Oxygen

- Diagram: Two red oxygen (O) atoms bonded together.
- Chemical formula: O₂
- Element or compound?: Element (only oxygen atoms)

✔ Answer:
- Chemical formula: O₂
- Element or compound: Element

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✔ Final Completed Table:

| Name of substance | Diagram of molecule | Chemical formula | Element or compound? |
|-------------------|---------------------|------------------|------------------------|
| Water | H–O–H | H₂O | Compound |
| Nitrogen | N≡N | N₂ | Element |
| Carbon dioxide | O=C=O | CO₂ | Compound |
| Ammonia | H₃N | NH₃ | Compound |
| Sulfur dioxide | O=S=O | SO₂ | Compound |
| Hydrogen | H–H | H₂ | Element |
| Hydrogen chloride | H–Cl | HCl | Compound |
| Oxygen | O=O | O₂ | Element |

> Note: The diagrams are simplified ball-and-stick models; actual bonding may differ slightly (e.g., double bonds in CO₂ and SO₂), but for this level, the formulas are correct.

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📝 Summary:

- Elements: Nitrogen (N₂), Hydrogen (H₂), Oxygen (O₂) — all consist of only one type of atom.
- Compounds: All others — made of two or more different atoms.

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