Worksheet starter|KS3 Chemistry - Free Printable

Let me work through this step by step.

I need to fill in two columns for each substance:
1. Chemical formula
2. Element or compound?

Let me go through each row:

1. Water
- Diagram shows: H-O-H (2 hydrogen atoms, 1 oxygen atom)
- Chemical formula: H₂O
- Contains two different elements (H and O), so it's a compound

2. Nitrogen
- Diagram shows: N-N (2 nitrogen atoms)
- Chemical formula: N₂
- Contains only one type of element (N), so it's an element

3. Carbon dioxide
- Diagram shows: O-C-O (1 carbon atom, 2 oxygen atoms)
- Chemical formula: CO₂
- Contains two different elements (C and O), so it's a compound

4. Ammonia
- Diagram shows: N with 3 H atoms around it (1 nitrogen, 3 hydrogen)
- Chemical formula: NH₃
- Contains two different elements (N and H), so it's a compound

5. Sulfur dioxide
- Diagram shows: O-S-O (1 sulfur atom, 2 oxygen atoms)
- Chemical formula: SO₂
- Contains two different elements (S and O), so it's a compound

6. Hydrogen
- Diagram shows: H-H (2 hydrogen atoms)
- Chemical formula: H₂
- Contains only one type of element (H), so it's an element

7. Hydrogen chloride
- Diagram shows: Cl-H (1 chlorine, 1 hydrogen)
- Chemical formula: HCl
- Contains two different elements (H and Cl), so it's a compound

8. Oxygen
- Diagram shows: O-O (2 oxygen atoms)
- Chemical formula: O₂
- Contains only one type of element (O), so it's an element

Let me verify my answers:
- Elements contain only ONE type of atom → Nitrogen (N₂), Hydrogen (H₂), Oxygen (O₂) ✓
- Compounds contain TWO OR MORE different types of atoms → Water (H₂O), Carbon dioxide (CO₂), Ammonia (NH₃), Sulfur dioxide (SO₂), Hydrogen chloride (HCl) ✓

All formulas look correct based on the diagrams shown.

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 |