P.1.1 Flashcards
What was the order ?
Democritus snd leucippus
2) dalton plum indestructible sphere model
3) Ja Thompson plum pudding model
4) Ernest Rutherford + Hans Geiger snd Ernest mars den gold foil= Rutherford nuclear atom model
5) Niels Bohr = mathematical diagrams
Greek
Thought they eventually if you kept cutting paper there Luke come a point where you wouldn’t be able to anymore, and that would be stop. Atomic means indivisible in Greek
Dalton?
1870ndwlton did experiments to see how elements combine, and could only explain his findings if he changed the atom model
1) that atoms were indestructible balls
2) that all the atomic in an element are the same
3) atoms in one element are different from atoms in every other element
Thompson model?
Working with cathode rays which are given out for hot metal rays.
He worked out these were 1/1000 mass of hydrogen atom, that it came from inside the atom and was negative- called it electron
Therefore he had to develop a model that made sense that atoms were overall neutral and had little negative elect indon.
Thus he proposed the plum pudding model, where there is a
Postbote mass cloud surrounded by negative elections embedded in it , making it neutral
Yet in 1909 what ja do
Alpha discovery
Fire st gold what they expect?
What actually happened and so what must have been done
First Rutherford worked out materials emit alpha or rifles that had POSITGE CHARGE, and to prove Thompson he decided to fire them at a gold foil.
(Good was used as it is thin sheet of gold essy ti make)
Based on Thompson , expected the alpha particles to go straight through, as it was thought the Positive Kasse was too spread out to repel the alpha particles .
However, while most did go through, some were deflected more than they expected, snd some even deflected right the angle it came at- which plum pudding did not explain. Thus it had to be revised
So what did the ja experiment mean then?
2) as most went through, meant it is empty space most of it
2) as some bounced back , Particularly in the middle, it was thought this were was some concentrated possible mass in the middle, that was tiny.
So the particle model was changed
1) mos for the mass of the atom is in a tiny positively charged nucleus , while electrons are “orbiting” around the nucleus .
But why was this wrong too, what did Bohr do to counter?
Scientists speculated that if it was orbiting then eventually the electrons is would spiral in to get attracted to the nucleus, thus meaning the atom become unstable
2) Bohr used mathematical evidence to prove that electrons should be fixed in energy levels and shells at certain distances from the nucleus , with fixed energy. His theory came close to what it is Today…
How big are atoms / molecules
And nucleus radius
1x10-10 diameter
Nucleus radios = 1-10 ^-15
