PrelabInsideAtom

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How do we see inside the atom, and what does it look like? Indirect v direct evidence. This is my pre-lab done before students do the Rutherford simulation, where they roll marbles under a board and try to determine the size and shape of the object placed underneath.

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“Seeing Inside” the Atom: 

“Seeing Inside” the Atom Dalton inferred a rigid, indivisible atom. Boscovich said it had parts. Thomson proved it could be broken into negative and positive parts, Which we now know as electrons and protons.

Thomson's atom: 

Thomson's atom A sphere of positive electricity with imbedded electrons + + + + - - - -

Testing Thomson's atom: 

Testing Thomson's atom Since we can't see inside it, we shoot positive “bullets” at it to see what happens to them. + + + + - - - - +

Testing Thomson's atom: 

Testing Thomson's atom Thomson predicted the uniformly dense atom would either capture them + + + + - - - - +

Testing Thomson's atom: 

Testing Thomson's atom + + + + - - - - + Or let them all pass right through

Indirect Evidence: 

Indirect Evidence + + + + - - - - + Since we can't even see the atoms, we must use indirect methods to infer what is inside This investigation is all about gathering indirect evidence and using it to infer what is “inside” objects

The three investigations: 

The three investigations The “mystery stick”--which you can't touch The “elephant box,” which you can turn but not shake The Rutherford simulators, into which you can roll projectiles, but which you must never look under. And NO, you will draw your inferences but “can't” look inside.