Valence Electrons worksheet asking students to determine the number of valence electrons in various atoms.

You're absolutely right — the image contains a worksheet titled "Valence Electrons", and it asks you to determine the number of valence electrons for 20 different elements.

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🔬 What Are Valence Electrons?

As stated in the worksheet:

> *Valence electrons are the electrons in the outermost energy level. The maximum number of valence electrons is 8.*

This is true for main-group elements (Groups 1, 2, and 13–18). For transition metals (like Fe, Zn, Cu), the definition can get trickier because they can use electrons from inner d-orbitals in bonding, but for introductory chemistry, we often still refer to the outermost s (and sometimes d) electrons as “valence” — though this varies by curriculum.

For this worksheet, since it’s likely aimed at middle/high school level, we’ll use the group number method for main-group elements and standard conventions for transition metals.

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## ✔ Step-by-Step Solution

We’ll go element by element and explain how we find the valence electrons.

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🧪 Main Group Elements (Groups 1, 2, 13–18)

For these, valence electrons = group number (for Groups 1–2) or group number - 10 (for Groups 13–18).

| Element | Symbol | Group | Valence Electrons | Reason |
|---------|--------|-------|-------------------|--------|
| 1. Fluorine | F | 17 | 7 | Group 17 → 17 - 10 = 7 |
| 2. Phosphorus | P | 15 | 5 | Group 15 → 15 - 10 = 5 |
| 3. Calcium | Ca | 2 | 2 | Group 2 → 2 |
| 4. Nitrogen | N | 15 | 5 | Group 15 → 5 |
| 5. Iron | Fe | 8 (transition) | 2 | Typically considered to have 2 valence electrons (4s²) |
| 6. Argon | Ar | 18 | 8 | Noble gas, full octet |
| 7. Potassium | K | 1 | 1 | Group 1 → 1 |
| 8. Helium | He | 18 | 2 | Only has 1 shell → 2 electrons total = valence |
| 9. Magnesium | Mg | 2 | 2 | Group 2 → 2 |
| 10. Sulfur | S | 16 | 6 | Group 16 → 16 - 10 = 6 |
| 11. Lithium | Li | 1 | 1 | Group 1 → 1 |
| 12. Zinc | Zn | 12 | 2 | Often considered to have 2 valence electrons (4s²) |
| 13. Carbon | C | 14 | 4 | Group 14 → 14 - 10 = 4 |
| 14. Iodine | I | 17 | 7 | Group 17 → 7 |
| 15. Oxygen | O | 16 | 6 | Group 16 → 6 |
| 16. Barium | Ba | 2 | 2 | Group 2 → 2 |
| 17. Aluminum | Al | 13 | 3 | Group 13 → 13 - 10 = 3 |
| 18. Hydrogen | H | 1 | 1 | Has 1 electron → valence = 1 |
| 19. Xenon | Xe | 18 | 8 | Noble gas, full octet |
| 20. Copper | Cu | 11 | 1 or 2 | Commonly 1 (due to [Ar] 4s¹ 3d¹⁰ configuration) |

> ⚠️ Note on Transition Metals:
> - Iron (Fe): Electron config [Ar] 4s² 3d⁶ → usually 2 valence electrons (from 4s).
> - Zinc (Zn): [Ar] 4s² 3d¹⁰ → stable, 2 valence electrons.
> - Copper (Cu): [Ar] 4s¹ 3d¹⁰ → only 1 electron in outermost shell → so 1 valence electron is most accurate for this context.

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## 📝 Final Answers (Fill-in-the-blank):

Here’s your completed worksheet:

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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## 💡 Quick Tip for Students:

To remember valence electrons easily:

- Group 1: 1
- Group 2: 2
- Group 13: 3
- Group 14: 4
- Group 15: 5
- Group 16: 6
- Group 17: 7
- Group 18: 8 (except He = 2)

Transition metals? Usually 2, except Cu, Ag, Au → often 1.

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✔ You’re all set! This worksheet is now fully solved with explanations. Let me know if you’d like electron configurations or Lewis dot diagrams too!