Electron Arrangement Worksheet | Atomic Model Activity - Free Printable

Let's solve this step by step. The task is to complete the Bohr models (electron arrangements) for each element and fill in the correct number of protons, neutrons, electrons, as well as the atomic number and atomic mass.

We’ll use standard atomic data from the periodic table. Here’s how we determine each value:

---

🔬 Key Concepts:

- Atomic Number = Number of protons = Number of electrons (in a neutral atom)
- Atomic Mass ≈ Protons + Neutrons (rounded to nearest whole number)
- Neutrons = Atomic Mass − Atomic Number
- Electrons are placed in shells following the 2, 8, 18... rule (but for these elements, only first two shells matter):
- First shell (closest to nucleus): holds up to 2 electrons
- Second shell: holds up to 8 electrons

---

Now let’s go through each element:

---

🟦 Hydrogen (H)

- Atomic Number: 1
- Atomic Mass: 1
- Protons: 1
- Electrons: 1
- Neutrons: 1 − 1 = 0

✔ Bohr model: 1 electron in the first shell

> Answer:
> - Protons: 1
> - Neutrons: 0
> - Electrons: 1
> - Atomic Number: 1
> - Atomic Mass: 1

---

🟦 Carbon (C)

- Atomic Number: 6
- Atomic Mass: 12
- Protons: 6
- Electrons: 6
- Neutrons: 12 − 6 = 6

Electron arrangement:
- First shell: 2 electrons
- Second shell: 4 electrons

✔ Bohr model: 2 in first shell, 4 in second

> Answer:
> - Protons: 6
> - Neutrons: 6
> - Electrons: 6
> - Atomic Number: 6
> - Atomic Mass: 12

---

🟦 Oxygen (O)

- Atomic Number: 8
- Atomic Mass: 16
- Protons: 8
- Electrons: 8
- Neutrons: 16 − 8 = 8

Electron arrangement:
- First shell: 2
- Second shell: 6

✔ Bohr model: 2 in first, 6 in second

> Answer:
> - Protons: 8
> - Neutrons: 8
> - Electrons: 8
> - Atomic Number: 8
> - Atomic Mass: 16

---

🟦 Sulfur (S)

- Atomic Number: 16
- Atomic Mass: 32
- Protons: 16
- Electrons: 16
- Neutrons: 32 − 16 = 16

Electron arrangement:
- First shell: 2
- Second shell: 8
- Third shell: 6

✔ Bohr model: 2 → 8 → 6

> Answer:
> - Protons: 16
> - Neutrons: 16
> - Electrons: 16
> - Atomic Number: 16
> - Atomic Mass: 32

---

🟦 Nitrogen (N)

- Atomic Number: 7
- Atomic Mass: 14
- Protons: 7
- Electrons: 7
- Neutrons: 14 − 7 = 7

Electron arrangement:
- First shell: 2
- Second shell: 5

✔ Bohr model: 2 → 5

> Answer:
> - Protons: 7
> - Neutrons: 7
> - Electrons: 7
> - Atomic Number: 7
> - Atomic Mass: 14

---

🟦 Boron (B)

- Atomic Number: 5
- Atomic Mass: 11
- Protons: 5
- Electrons: 5
- Neutrons: 11 − 5 = 6

Electron arrangement:
- First shell: 2
- Second shell: 3

✔ Bohr model: 2 → 3

> Answer:
> - Protons: 5
> - Neutrons: 6
> - Electrons: 5
> - Atomic Number: 5
> - Atomic Mass: 11

---

🟦 Helium (He)

- Atomic Number: 2
- Atomic Mass: 4
- Protons: 2
- Electrons: 2
- Neutrons: 4 − 2 = 2

Electron arrangement:
- First shell: 2 electrons (full)

✔ Bohr model: 2 in first shell

> Answer:
> - Protons: 2
> - Neutrons: 2
> - Electrons: 2
> - Atomic Number: 2
> - Atomic Mass: 4

---

✔ Final Answers Summary:

| Element | Protons | Neutrons | Electrons | Atomic Number | Atomic Mass |
|------------|---------|----------|-----------|---------------|-------------|
| Hydrogen | 1 | 0 | 1 | 1 | 1 |
| Carbon | 6 | 6 | 6 | 6 | 12 |
| Oxygen | 8 | 8 | 8 | 8 | 16 |
| Sulfur | 16 | 16 | 16 | 16 | 32 |
| Nitrogen | 7 | 7 | 7 | 7 | 14 |
| Boron | 5 | 6 | 5 | 5 | 11 |
| Helium | 2 | 2 | 2 | 2 | 4 |

---

💡 How to Draw the Bohr Models:

For each element:
1. Draw circles around the nucleus (blue dot).
2. Place electrons (dots or small circles) on the shells.
3. Fill inner shells first (max 2 in first, 8 in second, etc.).

Example: Carbon
- 2 electrons in first shell
- 4 electrons in second shell

---

You can now fill in the worksheet accordingly! Let me know if you'd like a visual guide or printable version.