1. History of the Atomic Model

2. write these dates down the left side of a new page – skip lines:
Do-It!
1000 B.C. 400 B.C Today
write these dates down the left side of a new page – skip lines:
Timeline

3. Make an entry next to each date
Make an entry next to each date. Draw a picture of the atomic model at each stage, to the far right of the corresponding date.

4. People have always been interested in what all of this "stuff" is made of.

5. Draw this for the atomic model:
A Long time ago (about 1000 B.C.) the Greek's way of knowing explained that everything was made of 4 elements BC in Greece
Anciently, the Greek’s way of knowing explained that everything was made of combinations of 4 elements:
Draw this for the atomic model:
Earth
Wind
Fire
Water

6. 1000 B.C. Only 4 elements 400 B.C. 1780 1805 1808 1897 1904 1911 1913 1930 1932 1942 Today

7. That's right – the same as the ELEMENT skateboard brand logo: earth, wind, fire, water

8. For example, a tree must have earth, water, and fire inside: it grew from the earth, it required water to live, and it produced fire when it was very hot.

9. These ideas stood for a long time, until about 400 B. C
These ideas stood for a long time, until about 400 B.C. when a Greek guy named Democritus proposed a different idea.

10. Democritus thought that the universe was made of empty space and tiny bits of stuff. He thought that these bits of stuff were so tiny that they couldn't be cut any smaller, so the Greeks named them "atoms." Atom means "cannot be divided" in Greek.

11. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles

12. Democritus' idea that matter is made up of tiny particles and empty space was a good start, but many questions still needed to be answered…

13. Loading…Please Wait
not much happening on the atomic theory front for the next 300 years…

14. Fast forward to the 1780's. A French chemist named Lavoiser showed that matter can't be "used-up."

15. He sealed a splinter of wood inside a bottle with an ignitor
He sealed a splinter of wood inside a bottle with an ignitor. He weighed the whole thing, then lit the wood on fire. He waited until there was nothing but ashes, then weighed the bottle again.

16. What do you think happened. That's right – it weighed exactly the same
What do you think happened? That's right – it weighed exactly the same. The atoms in the wood were not used up, they were just converted to invisible gas.

17. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter

18. Scientists then changed their ideas in light of this new evidence, but they still wondered what atoms actually looked like. No one then (or even now) has actually seen an atom.

19. In 1805, a British chemist named John Dalton did experiments which concluded that each element is made of atoms, and that all atoms are alike, except that different elements have different masses.

20. Dalton thought that atoms were tiny solid spheres – like billiard balls, but that they came in different sizes.

21. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter 1805 Different elements have different masses

22. Ninety years later, J.J. Thompson built on Dalton's ideas and conducted experiments which showed that atoms had negative charged particles that he named "electrons."

23. Thompson's model was sorta like a blueberry muffin
Thompson's model was sorta like a blueberry muffin. The atom-muffin had electron-blueberries scattered throughout the atom and also stuck to the outside.

24. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter 1805 Different elements have different masses 1897 Atoms contain negative electrons

25. In 1904, a Japanese physicist named Nagaoka built on the work of Thompson and Dalton and proposed that the center of an atom had a positive charge and the electrons on the outside had a negative charge.

26. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter 1805 Different elements have different masses 1897 Atoms contain negative electrons 1904 Atoms are neutrally charged

27. Just 7 years later, another Brit named Ernest Rutheford was doing his own experiments. These trials presented evidence that the atom is mostly empty space, and the electrons are far, far away from the nucleus.

28. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter 1805 Different elements have different masses 1897 Atoms contain negative electrons 1904 Atoms are neutral charged 1911 Atoms are mostly empty space Today

29. Rutheford's model is still used sometimes today
Rutheford's model is still used sometimes today. Can you name the famous cartoon character based on his model?

30. In 1913 in Holland, Niels Bohr proposed a slightly enhanced model that showed the electrons orbiting the nucleus in layers, or shells. He said that atoms give off energy when electrons move between layers.

31. Boh'r model is also in use today (sometimes) when we need to picture how the electrons are arranged .

32. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter 1805 Different elements have different masses 1897 Atoms contain negative electrons 1904 Atoms are neutral charged 1911 Atoms are mostly empty space Electrons orbit in valence shells

33. Back to the British again, in 1932 James Chadwick discovered that there was something else in the nucleus besides protons, but they didn't have a charge – they were neutral. He named these blobs NEUTRONS. We had to re-write all of the textbooks again!

34. 1000 B.C. Only 4 elements 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter 1805 Different elements have different masses 1897 Atoms contain negative electrons 1904 Atoms are neutral charged 1911 Atoms are mostly empty space Electrons orbit in valence shells 1923 Nucleus has protons and neutrons

35. This model of the atom, with electrons that orbit around the nucleus in little "racetracks" was the one I learned when I was in high school. (It wasn't THAT long ago!)

36. Currently, we think that the electrons don't travel in definite ovals, they zing all over the place and they're moving so fast that they are just a blur. Electrons make a "cloud" around the nucleus that has several layers. Kinda like bees buzzing around a hive.

37. Our current model sorta looks like a clump of particles within a balloon within a balloon within a balloon…

38. Scientists have also concluded that protons and neutrons have even tinier particles inside called quarks, held together by gluons. But this is another story….

39. 400 B.C. Matter is made of tiny particles 1780 Conservation of Matter 1805 Different elements have different masses 1897 Atoms contain negative electrons 1904 Atoms are neutral charged 1911 Atoms are mostly empty space Electrons orbit in valence shells 1923 Nucleus has protons and neutrons Now Electron cloud, quarks, gluons, dark matter

40. After all of this talk, here are the five big ideas: (write these down)

41. 1- Atoms are so small that no one has ever seen them – not even with microscopes. (The best we have been able to see is a bunch of lumps in a tunneling electron microscope.)

42. 2- We make models to help us understand what atoms look like.

43. 3- We keep changing the model of the atom as new evidence is presented.

44. 4- Scientists base their experiments and opinions on the work of others that came before them.

45. 5- We have a better model of the atom today because we have better technology – not because we are smarter, or use better methods. (Those other guys were pretty smart too!)

46. THE END (Or is it? Do you think we will ever have a different model of the atom?)