Atomic Structure Flashcards
What is the plum pudding theory?
That the atom was a positive nucleus with negative electrons( slices of plum) stuck throughout it.
How did Rutherford and Marsden test the plum pudding theory?
They fired alpha particles at a piece of gold leaf, expecting them to all be slightly repelled
What happened when R and M fired the alpha particles at the gold leaf?
> Most passed straight through- meaning that most of the atom is empty space
> some were deflected by varying degrees
- the atom has a positive centre
> some came straight back
- the centre is very dense
Why was R+M’s test done in a vacuum?
So that no air particles would deflect and interfere with the results.
Who devised and tested the ‘plum pudding’ theory?
> Rutherford and Marsden
Why do scientists sometime change theories?
> because they discover new evidence
What is the:
> charge
mass
materials
Of an alpha particle?
> charge is +2
> mass is 4
> 2 neutrons and 2 protons
What is the:
> charge
mass
materials
of a beta particle?
> charge is -1
> mass is close to 0
> it is made of 1 electron
What is the:
> charge
mass
materials
of gamma rays?
> 0
> 0
> it is a wave on the Em spectrum
What can an alpha particle be stopped by?
> a piece of paper / skin
What can a beta particle be stopped by?
> a few mm of aluminium
What can a gamma ray be stopped by?
> +5cm of lead
or +1m of concrete
What is the range of a gamma ray in air?
> unlimited
What is the range of a beta particle in air?
> 1m
What is the range of an alpha particle in air?
> a few cm
