Valence Electrons interactive worksheet - Free Printable

Let's solve this step by step. The task is to determine the number of valence electrons for each given atom.

🔍 What are Valence Electrons?

Valence electrons are the electrons in the outermost energy level (shell) of an atom. They are crucial in chemical bonding.

For main group elements (Groups 1, 2, and 13–18), you can find the number of valence electrons by looking at the group number:
- Group 1: 1 valence electron
- Group 2: 2 valence electrons
- Group 13: 3 valence electrons
- Group 14: 4 valence electrons
- Group 15: 5 valence electrons
- Group 16: 6 valence electrons
- Group 17: 7 valence electrons
- Group 18: 8 valence electrons (except He, which has 2)

For transition metals (Groups 3–12) like Iron (Fe), Zinc (Zn), Copper (Cu), the number of valence electrons is not always straightforward because they can have variable oxidation states. However, we often consider the electrons in the outermost s and d orbitals.

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Now let’s go through each element:

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✔ Answers with Explanations:

1. Fluorine (F) – Group 17 → 7 valence electrons
2. Phosphorus (P) – Group 15 → 5 valence electrons
3. Calcium (Ca) – Group 2 → 2 valence electrons
4. Nitrogen (N) – Group 15 → 5 valence electrons
5. Iron (Fe) – Transition metal (Group 8). It has 2 valence electrons (from 4s²) but can lose more. For simplicity, we say 2 or sometimes 3, but 2 is standard for valence electrons in basic chemistry.
→ 2 (commonly accepted)
6. Argon (Ar) – Group 18 → 8 valence electrons (full octet)
7. Potassium (K) – Group 1 → 1 valence electron
8. Helium (He) – Group 18, but only 1s² → 2 valence electrons (exception)
9. Magnesium (Mg) – Group 2 → 2 valence electrons
10. Sulfur (S) – Group 16 → 6 valence electrons
11. Lithium (Li) – Group 1 → 1 valence electron
12. Zinc (Zn) – Transition metal (Group 12). Has full d¹⁰ and 4s² → 2 valence electrons
13. Carbon (C) – Group 14 → 4 valence electrons
14. Iodine (I) – Group 17 → 7 valence electrons
15. Oxygen (O) – Group 16 → 6 valence electrons
16. Barium (Ba) – Group 2 → 2 valence electrons
17. Aluminum (Al) – Group 13 → 3 valence electrons
18. Hydrogen (H) – Group 1 → 1 valence electron
19. Xenon (Xe) – Group 18 → 8 valence electrons
20. Copper (Cu) – Transition metal (Group 11). Electron configuration ends in 4s¹ 3d¹⁰ → 1 valence electron (loses 4s¹ easily)

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✔ Final Answer Key:

| Number | Element | Valence Electrons |
|--------|-------------|-------------------|
| 1 | Fluorine (F) | 7 |
| 2 | Phosphorus (P) | 5 |
| 3 | Calcium (Ca) | 2 |
| 4 | Nitrogen (N) | 5 |
| 5 | Iron (Fe) | 2 |
| 6 | Argon (Ar) | 8 |
| 7 | Potassium (K) | 1 |
| 8 | Helium (He) | 2 |
| 9 | Magnesium (Mg) | 2 |
| 10 | Sulfur (S) | 6 |
| 11 | Lithium (Li) | 1 |
| 12 | Zinc (Zn) | 2 |
| 13 | Carbon (C) | 4 |
| 14 | Iodine (I) | 7 |
| 15 | Oxygen (O) | 6 |
| 16 | Barium (Ba) | 2 |
| 17 | Aluminum (Al) | 3 |
| 18 | Hydrogen (H) | 1 |
| 19 | Xenon (Xe) | 8 |
| 20 | Copper (Cu) | 1 |

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🧠 Summary Tips:

- Use the periodic table group number for main-group elements.
- Noble gases (except He) have 8 valence electrons.
- Helium has only 2 (1s²).
- Transition metals usually have 2 valence electrons (from ns²), though exceptions exist.
- Hydrogen is special: 1 valence electron.

Let me know if you'd like a printable version or explanation for any specific element!