Shizah Ahmed - Atomic Theory Activity | Descarca gratis PDF ... - Free Printable

Let's solve this Atomic Theory Timeline activity step by step. The goal is to match each scientist with their correct contribution, discovery, and year in the timeline of atomic theory development.

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🔍 Step 1: Understand the Goal

We need to:
- Match each scientist (Democritus, John Dalton, J.J. Thomson, Ernest Rutherford, Bohr, Werner Heisenberg) with:
- Their year of key contribution.
- Their discovery or model.
- The correct image of their atomic model.
- Fill in the timeline in chronological order.

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🧩 Step 2: Organize Scientists by Year

Here are the scientists and their correct years:

| Scientist | Year | Contribution |
|---------|------|-------------|
| Democritus | 460 BC | Proposed that matter is made of tiny indivisible particles called "atoms" |
| John Dalton | 1808 | Developed the modern atomic theory – all matter made of atoms, elements have identical atoms, etc. |
| J.J. Thomson | 1904 | Discovered the electron; proposed the plum pudding model |
| Ernest Rutherford | 1911 | Discovered the nucleus; proposed the planetary model |
| Niels Bohr | 1913 | Proposed that electrons orbit the nucleus in fixed energy levels (Bohr model) |
| Erwin Schrödinger / Werner Heisenberg | 1926 | Developed the quantum mechanical model (electron cloud); Heisenberg’s uncertainty principle |

> Note: The name list says "Erwin Schrodinger" but shows Werner Heisenberg in the picture. This might be a typo. But since the image shows Heisenberg, and he contributed in 1926, we’ll go with him for 1926.

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✔ Step 3: Match Each Box Correctly

Now let’s fill in the timeline from left to right.

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#### 1. Democritus – 460 BC
- Contribution:
- Everything was made from tiny particles surrounded by empty space.
- Vary in size and shape depending on composition.
- Indivisible.
- Model: First image (particles like spheres connected) – represents ancient atomism.

✔ Already filled in correctly.

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#### 2. John Dalton – 1808
- Contribution:
- Atomic Theory:
1. All matter is made from atoms.
2. All atoms of a given element are identical in mass.
3. Compounds are formed by combining elements.
4. Chemical reactions involve rearrangement of atoms.
- Model: Second image – solid sphere with dots (representing atoms).
> This is Dalton’s model – atoms as indestructible spheres.

✔ Matches the description.

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#### 3. J.J. Thomson – 1904
- Contribution:
- He discovered electrons (called cathode rays).
- Proposed the plum pudding model – electrons embedded in a positive "pudding".
- Model: Third image – red and blue dots in a sphere → Thomson’s model.

✔ Matches.

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#### 4. Ernest Rutherford – 1911
- Contribution:
- He discovered the nucleus of the atom through gold foil experiment.
- Proposed the planetary model – electrons orbit a dense nucleus.
- Model: Fourth image – nucleus in center with electrons orbiting → Rutherford model.

✔ Matches.

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#### 5. Bohr – 1913
- Contribution:
- He discovered that electrons orbit the nucleus in fixed energy levels.
- Improved Rutherford’s model with quantized orbits.
- Model: Fifth image – circular orbits with labels (n=1, n=2) → Bohr model.

✔ Matches.

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#### 6. Werner Heisenberg – 1926
- Contribution:
- He discovered the quantum theory of atoms that it's not certain where an electron is positioned.
- Introduced the uncertainty principle.
- Part of the electron cloud model (developed alongside Schrödinger).
- Model: Sixth image – blurry cloud around nucleus → electron cloud model.

✔ Matches.

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📌 Final Timeline (Left to Right):

| Scientist | Year | Contribution |
|------------------|----------|--------------|
| Democritus | 460 BC | Indivisible particles; everything made of tiny particles |
| John Dalton | 1808 | Atomic theory: atoms combine to form compounds |
| J.J. Thomson | 1904 | Discovered electrons; plum pudding model |
| Ernest Rutherford| 1911 | Discovered nucleus; planetary model |
| Bohr | 1913 | Electrons orbit in fixed energy levels |
| Werner Heisenberg| 1926 | Quantum theory; electron position uncertain; electron cloud |

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🖼️ Model Images Matched:

1. Democritus: Spheres connected (ancient atoms)
2. Dalton: Solid sphere (simple atom)
3. Thomson: Red/blue dots in sphere (plum pudding)
4. Rutherford: Nucleus + orbiting electrons (planetary)
5. Bohr: Circular orbits labeled n=1, n=2
6. Heisenberg: Cloud around nucleus (electron cloud)

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✔ Summary: How Scientific Models Evolved

Each new discovery led to a revision of the atomic model:
- Democritus: Philosophical idea of atoms.
- Dalton: First scientific atomic theory.
- Thomson: Found electrons → atoms aren’t solid.
- Rutherford: Found nucleus → most mass concentrated.
- Bohr: Electrons in fixed orbits → explained spectra.
- Heisenberg/Schrödinger: Quantum mechanics → electrons exist in probability clouds.

This shows how science builds on evidence — models change with new data.

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📝 Final Answer:

The timeline is now complete and accurate when arranged as:

1. Democritus – 460 BC – Indivisible particles
2. John Dalton – 1808 – Atomic theory
3. J.J. Thomson – 1904 – Discovered electrons; plum pudding model
4. Ernest Rutherford – 1911 – Discovered nucleus; planetary model
5. Bohr – 1913 – Electrons orbit in energy levels
6. Werner Heisenberg – 1926 – Quantum theory; electron cloud

All images and descriptions match correctly.

✔ Task Complete!

You can now submit this completed timeline to Google Classroom.