Lewis electron valence worksheet - Free Printable

Let's solve each part of this Valence Electron Worksheet step by step and explain the solutions clearly.

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1. How many electrons are in the following elements?

This question is asking for the total number of electrons in a neutral atom of each element (which equals the atomic number).

| Element | Atomic Number | Electrons |
|-------------|----------------|-----------|
| A. Carbon | 6 | 6 |
| B. Chlorine | 17 | 17 |
| C. Indium | 49 | 49 |
| D. Calcium | 20 | 20 |
| E. Tungsten | 74 | 74 |
| F. Antimony | 51 | 51 |

✔ Answers:
- A. Carbon → 6
- B. Chlorine → 17
- C. Indium → 49
- D. Calcium → 20
- E. Tungsten → 74
- F. Antimony → 51

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2. Draw Lewis Structures for each of the following elements. How many electrons are in their outer shells?

Lewis structures show valence electrons as dots around the element symbol.

We'll determine valence electrons based on group number:

| Element | Group | Valence Electrons | Lewis Structure (dots) |
|-------------|-------|--------------------|------------------------|
| A. Silicon | 14 | 4 | Si with 4 dots (one on each side) |
| B. Potassium| 1 | 1 | K with one dot |
| C. Sulfur | 16 | 6 | S with 6 dots (two pairs, two singles) |
| D. Boron | 13 | 3 | B with 3 dots |
| E. Beryllium| 2 | 2 | Be with two dots |
| F. Argon | 18 | 8 | Ar with 8 dots (full octet) |

✔ Number of electrons in outer shell (valence electrons):
- A. Silicon → 4
- B. Potassium → 1
- C. Sulfur → 6
- D. Boron → 3
- E. Beryllium → 2
- F. Argon → 8

> 💡 *Note: For Lewis structures, you draw the element symbol and place dots around it to represent valence electrons.*

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3. Circle the valence electrons only. How many valence electrons does each atom have?

We are given electron shell diagrams for:
- F (Fluorine)
- Cl (Chlorine)
- Br (Bromine)
- I (Iodine)

These are all Group 17 (Halogens) — they have 7 valence electrons.

Let’s analyze:

#### Fluorine (F):
- Electron configuration: 2, 7
- Outermost shell has 7 electrons
- ✔ Valence electrons: 7

#### Chlorine (Cl):
- Configuration: 2, 8, 7
- Outer shell has 7 electrons
- ✔ Valence electrons: 7

#### Bromine (Br):
- Configuration: 2, 8, 18, 7
- Outermost shell has 7 electrons
- ✔ Valence electrons: 7

#### Iodine (I):
- Configuration: 2, 8, 18, 18, 7
- Outermost shell has 7 electrons
- ✔ Valence electrons: 7

> 🔁 All halogens have 7 valence electrons.

✔ Answer: Each has 7 valence electrons.

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4. Finish the sentence: Elements in the same group have the same number of ________ electrons.

✔ Answer: Valence electrons

> ✔️ Elements in the same group (vertical column) of the periodic table have the same number of valence electrons.

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5. Fill in the electrons for the following elements. Use your work to answer how many valence electrons each element has.

We need to fill orbital diagrams and count valence electrons.

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#### Example: C (carbon)
Given:
`1S↑↓ 2S↑↓ 2P↑ ↑ ___`
→ So:
- 1s², 2s², 2p² → total valence electrons = 4 (from 2nd shell)

✔ #valence electrons = 4

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#### He (Helium)
- Atomic number: 2
- Configuration: 1s²
- No 2s or 2p orbitals filled
- Valence electrons: 2 (but helium is an exception — full 1s shell)

```
He: 1S ↑↓ 2S ____ 3S ____ 3P _____
```

✔ Number of valence electrons in helium = 2

> ❗ Note: Even though helium is in Group 18, it only has 2 valence electrons because its first shell is full.

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#### Cl (Chlorine)
- Atomic number: 17
- Configuration: 1s² 2s² 2p⁶ 3s² 3p⁵
- Valence electrons: 3s² 3p⁵ → 7 electrons

```
Cl: 1S ↑↓ 2S ↑↓ 2P ↑↓ ↑↓ ↑↓ 3S ↑↓ 3P ↑↓ ↑↓ ↑
```

✔ Number of valence electrons in chlorine = 7

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#### Li (Lithium)
- Atomic number: 3
- Configuration: 1s² 2s¹
- Valence electrons: 2s¹ → 1 electron

```
Li: 1S ↑↓ 2S ↑ 2P ____ 3S ____ 3P _____
```

✔ Number of valence electrons in lithium = 1

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#### B (Boron)
- Atomic number: 5
- Configuration: 1s² 2s² 2p¹
- Valence electrons: 2s² 2p¹ → 3 electrons

```
B: 1S ↑↓ 2S ↑↓ 2P ↑ 3S ____ 3P _____
```

✔ Number of valence electrons in boron = 3

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#### F (Fluorine)
- Atomic number: 9
- Configuration: 1s² 2s² 2p⁵
- Valence electrons: 2s² 2p⁵ → 7 electrons

```
F: 1S ↑↓ 2S ↑↓ 2P ↑↓ ↑↓ ↑ 3S ____ 3P _____
```

✔ Number of valence electrons in fluorine = 7

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#### Ar (Argon)
- Atomic number: 18
- Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶
- Valence electrons: 3s² 3p⁶ → 8 electrons

```
Ar: 1S ↑↓ 2S ↑↓ 2P ↑↓ ↑↓ ↑↓ 3S ↑↓ 3P ↑↓ ↑↓ ↑↓
```

✔ Number of valence electrons in argon = 8

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✔ Final Answers for Question 5:

| Element | Orbital Diagram (filled) | Valence Electrons |
|--------|----------------------------|-------------------|
| He | 1S ↑↓ | 2 |
| Cl | 1S ↑↓ 2S ↑↓ 2P ↑↓ ↑↓ ↑↓ 3S ↑↓ 3P ↑↓ ↑↓ ↑ | 7 |
| Li | 1S ↑↓ 2S ↑ | 1 |
| B | 1S ↑↓ 2S ↑↓ 2P ↑ | 3 |
| F | 1S ↑↓ 2S ↑↓ 2P ↑↓ ↑↓ ↑ | 7 |
| Ar | 1S ↑↓ 2S ↑↓ 2P ↑↓ ↑↓ ↑↓ 3S ↑↓ 3P ↑↓ ↑↓ ↑↓ | 8 |

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🟩 Summary of All Answers:

#### 1. Total Electrons:
- A. Carbon → 6
- B. Chlorine → 17
- C. Indium → 49
- D. Calcium → 20
- E. Tungsten → 74
- F. Antimony → 51

#### 2. Valence Electrons (Outer Shell):
- A. Silicon → 4
- B. Potassium → 1
- C. Sulfur → 6
- D. Boron → 3
- E. Beryllium → 2
- F. Argon → 8

#### 3. Valence Electrons from Diagrams:
- F → 7
- Cl → 7
- Br → 7
- I → 7

#### 4. Sentence Completion:
- Elements in the same group have the same number of valence electrons.

#### 5. Electron Configurations & Valence Electrons:
| Element | Valence Electrons |
|--------|-------------------|
| He | 2 |
| Cl | 7 |
| Li | 1 |
| B | 3 |
| F | 7 |
| Ar | 8 |

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✔ This worksheet reinforces understanding of:
- Atomic structure
- Periodic trends
- Valence electrons
- Lewis structures
- Orbital filling

Let me know if you'd like a printable version or visual diagrams!