exploring the world of atoms Presentation - 7th grade.pptx

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1. Exploring the World of Atoms

2. Introduction to Atoms What are atoms? Why are they important? Who first proposed the idea of atoms?

3. Democritus: The First Philosopher Lived around 440 BCE. Suggested everything is made of tiny particles. Called these particles "atomos," meaning indivisible.

4. Aristotle's View Aristotle disagreed with Democritus. Believed matter was made of four elements: earth, wind, water, and fire. Most scientists followed Aristotle's ideas for many years.

5. John Dalton's Contribution In 1808, John Dalton challenged Aristotle's theory. Showed that substances break down into the same elements. Proposed that atoms combine in specific ways to form compounds.

6. Atoms cannot be created or destroyed. Each element has atoms of a particular size and mass. Dalton lived modestly as a Quaker teacher.

7. J.J. Thompson's Discovery In 1897, discovered the electron. Proposed the "chocolate chip cookie" model of the atom. Atoms are made of positive matter with negative electrons inside.

8. Ernest Rutherford's Experiment Conducted experiments with gold foil and alpha particles. Found that atoms are mostly empty space. Discovered the nucleus at the center of the atom.

9. Rutherford's Findings Most of the atom's mass is in the nucleus. Nucleus is positively charged. Electrons are scattered around the nucleus.

10. Niels Bohr's Model Expanded on Rutherford's model in 1913. Proposed electrons orbit the nucleus at fixed distances. Electrons can jump between energy levels.

11. Challenges to Bohr's Model Electrons behave like waves, not just particles. Heisenberg's uncertainty principle: can't know exact position and speed of electrons.

12. The Quantum Model Electrons exist in ranges of possible locations. This model is complex and still being studied. It helps explain many phenomena in physics and chemistry.

13. Celebrating Atomic Theory Atomic theory has evolved over centuries. Understanding of atoms continues to change. Let's celebrate the triumph of atomic theory!

14. Atoms and Light Electrons absorb or release energy as they move. This energy appears as different colors of light. Think about the colors you see around you!

15. Democritus: A Visionary Imagine Democritus watching today. He would be proud that his ideas were proven right. How do you think he would feel about modern science?

16. Reviewing Key Concepts What are atoms made of? Who were the key figures in atomic theory? How has our understanding of atoms changed?

17. Discussion Questions Why do you think Democritus's ideas were ignored for so long? How do you think Dalton's work changed science? What do you find most interesting about atomic theory?

18. Conclusion Atoms are the building blocks of everything. Our understanding of them has evolved greatly. Keep exploring the wonders of science!