Atomic theory timeline.pptx - Atomic theory scientist and timeline ... - Free Printable

It looks like you've uploaded an image of a timeline titled "Atomic theory scientist and timeline" by "Jourdyn.M." The timeline highlights key milestones in the development of atomic theory from 400 BCE to 1911 CE, with notable scientists and their contributions.

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🔍 Overview of the Atomic Theory Timeline

This timeline traces the evolution of human understanding of atoms—from ancient philosophical ideas to modern scientific models.

Let’s break down the major points likely included (based on standard historical knowledge):

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#### 📅 400 BCE – Democritus
- Scientist: Democritus (Greek philosopher)
- Contribution: Proposed the idea that all matter is made of tiny, indivisible particles called "atomos" (meaning "uncuttable").
- Key Idea: Atoms are eternal, indestructible, and vary in shape and size.
- Note: This was a philosophical idea, not based on experiments.

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#### 📅 1804 – John Dalton
- Scientist: John Dalton
- Contribution: Developed the first scientific atomic theory.
- Key Points:
- All matter is composed of tiny, indivisible atoms.
- Atoms of the same element are identical in mass and properties.
- Atoms combine in simple whole-number ratios to form compounds.
- Chemical reactions involve rearrangement of atoms.
- Significance: Laid the foundation for modern chemistry.

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#### 📅 1869 – Dmitri Mendeleev
- Scientist: Dmitri Mendeleev
- Contribution: Created the periodic table of elements.
- Key Idea: Elements could be arranged by increasing atomic mass and grouped by similar chemical properties.
- Impact: Predicted the existence of undiscovered elements (e.g., gallium, germanium).

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#### 📅 1897 – J.J. Thomson
- Scientist: J.J. Thomson
- Contribution: Discovered the electron using cathode ray tube experiments.
- Model: Proposed the "plum pudding model" — atoms are spheres of positive charge with electrons embedded like plums in a pudding.
- Significance: First evidence that atoms are divisible.

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#### 📅 1911 – Ernest Rutherford
- Scientist: Ernest Rutherford
- Contribution: Conducted the gold foil experiment.
- Discovery: Most of the atom is empty space; positive charge and mass are concentrated in a small nucleus.
- Model: Introduced the nuclear model of the atom.
- Impact: Led to the discovery of the nucleus and protons.

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✔ Summary of Key Developments:

| Year | Scientist | Contribution |
|------|------------------|-------------------------------------------|
| 400 BCE | Democritus | Concept of indivisible atoms |
| 1804 | John Dalton | Scientific atomic theory |
| 1869 | Mendeleev | Periodic table |
| 1897 | J.J. Thomson | Discovery of electron; plum pudding model |
| 1911 | Rutherford | Nuclear model; discovery of nucleus |

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🧠 Why This Timeline Matters:

This progression shows how scientific understanding evolves through observation, experimentation, and revision. Each scientist built upon previous work, leading to our current quantum mechanical model of the atom.

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