Atom Timeline worksheet - Free Printable

Let’s solve this step by step.

We are given a matching task: on the left, we have atomic models with their names and scientists + years. On the right, we have diagrams of atoms and descriptions of what was discovered or proposed in each model.

Our job is to match each model (left) with its correct diagram and description (right).

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Step 1: Look at the Solid sphere model (Dalton, 1803)
→ Dalton thought atoms were tiny solid spheres, like billiard balls.
→ The bottom-right diagram shows a plain yellow sphere — that matches “solid sphere”.
→ The description next to it says: “said that atoms are tiny solid spheres. Atoms of different elements are of different sizes.” → That’s Dalton!
✔ So, Solid sphere model → Bottom row (plain sphere + that description)

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Step 2: Plum pudding model (Thomson, 1897)
→ Thomson discovered the electron. He imagined the atom as a positive “pudding” with negative electrons stuck in it like plums.
→ Look for a diagram with a big positive sphere and small negative dots inside.
→ Third row from top on the right: orange sphere with plus sign and minus signs around → that’s plum pudding.
→ Description says: “discovered the electron” → Yes, Thomson did that.
✔ Plum pudding model → Third row from top (orange sphere with + and -)

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Step 3: Nuclear model (Rutherford, 1911)
→ Rutherford did the gold foil experiment. He found that atoms have a tiny, dense, positively charged nucleus in the center.
→ Top-right diagram: has a red + in the center, and electrons orbiting far away → that’s Rutherford’s nuclear model.
→ Description: “discovered the nucleus and that it had a positive charge.” → Perfect match.
✔ Nuclear model → Top row (central + with orbits)

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Step 4: Planetary model (Bohr, 1913)
→ Bohr said electrons move in specific orbits (like planets around the sun).
→ Fourth row from top on the right: shows labeled “Electron” moving in circular paths around “Nucleus” → that’s Bohr’s model.
→ Description: “discovered that electrons move around the nucleus in specific orbits.” → Exactly!
✔ Planetary model → Fourth row (labeled orbits)

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Step 5: Quantum model (Schrödinger, 1926)
→ Schrödinger’s model says electrons don’t follow fixed paths — they exist in “clouds” where you’re likely to find them.
→ Second row from top on the right: shows a fuzzy cloud around the nucleus, labeled “Neutron”, “Proton”, and says “Electrons form an electron cloud” → That’s quantum model.
✔ Quantum model → Second row (electron cloud)

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Now let’s write the final matched pairs clearly:

- Solid sphere model (Dalton, 1803) → Plain sphere + “said that atoms are tiny solid spheres...”
- Plum pudding model (Thomson, 1897) → Orange sphere with + and - + “discovered the electron”
- Nuclear model (Rutherford, 1911) → Central + with orbits + “discovered the nucleus...”
- Planetary model (Bohr, 1913) → Labeled orbits + “electrons move... in specific orbits”
- Quantum model (Schrödinger, 1926) → Electron cloud + “Electrons form an electron cloud”

Final Answer:
Match each model to its correct diagram and description as follows:

- Solid sphere model (Dalton, 1803) → Bottom diagram (plain sphere) with description: “said that atoms are tiny solid spheres. Atoms of different elements are of different sizes.”
- Plum pudding model (Thomson, 1897) → Third diagram from top (orange sphere with + and -) with description: “discovered the electron”
- Nuclear model (Rutherford, 1911) → Top diagram (central + with orbits) with description: “discovered the nucleus and that it had a positive charge.”
- Planetary model (Bohr, 1913) → Fourth diagram from top (labeled orbits) with description: “discovered that electrons move around the nucleus in specific orbits.”
- Quantum model (Schrödinger, 1926) → Second diagram from top (electron cloud) with description: “Electrons form an electron cloud”