Worksheet starter|KS3 Chemistry - Free Printable

Let’s go row by row and fill in the missing parts of the table.

We need to write:
1. The chemical formula — this is made from the symbols of the atoms shown in the diagram.
2. Whether it’s an element or compound —
- An element has only one type of atom (like O₂, N₂).
- A compound has two or more different types of atoms (like H₂O, CO₂).

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Row 1: Water
- Diagram shows: 2 Hydrogen (H) + 1 Oxygen (O) → Formula = H₂O
- Two different elements → Compound

Row 2: Nitrogen
- Diagram shows: 2 Nitrogen (N) atoms → Formula = N₂
- Only one type of atom → Element

Row 3: Carbon dioxide
- Diagram shows: 1 Carbon (C) + 2 Oxygen (O) → Formula = CO₂
- Two different elements → Compound

Row 4: Ammonia
- Diagram shows: 1 Nitrogen (N) + 3 Hydrogen (H) → Formula = NH₃
- Two different elements → Compound

Row 5: Sulfur dioxide
- Diagram shows: 1 Sulfur (S) + 2 Oxygen (O) → Formula = SO₂
- Two different elements → Compound

Row 6: Hydrogen
- Diagram shows: 2 Hydrogen (H) atoms → Formula = H₂
- Only one type of atom → Element

Row 7: Hydrogen chloride
- Diagram shows: 1 Hydrogen (H) + 1 Chlorine (Cl) → Formula = HCl
- Two different elements → Compound

Row 8: Oxygen
- Diagram shows: 2 Oxygen (O) atoms → Formula = O₂
- Only one type of atom → Element

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Final Answer:

| Name of substance | Chemical formula | Element or compound? |
|------------------------|------------------|-----------------------|
| Water | H₂O | Compound |
| Nitrogen | N₂ | Element |
| Carbon dioxide | CO₂ | Compound |
| Ammonia | NH₃ | Compound |
| Sulfur dioxide | SO₂ | Compound |
| Hydrogen | H₂ | Element |
| Hydrogen chloride | HCl | Compound |
| Oxygen | O₂ | Element |