rutherford’s experiment how he found out how atoms were put together
TRANSCRIPT
RUTHERFORD’S EXPERIMENT
How he found out how atoms were put
together
In 1911 it was known that things were made from atoms, and that atoms had positive (+) and negative (-) charges.
They thought that atoms were solid little balls of
positive charge, with even smaller electrons of
negative charge stuck in them.
This was the “Plum Pudding” model
Spread out positive charge
Electron (negative charge)
In 1911 Rutherford designed an experiment to
find out about the structure of an atom. He fired alpha particles at a very thin piece of gold
leaf.
gold leaf
detector
alpha particles
He expected them all to go straight through…….
gold leaf
detector
alpha particles
But some bounced straight back………….
gold leaf
detector
alpha particles
And some were deflected………….
From this he worked out two things……..
1. Atoms were mostly empty space apart from a
solid centre, or nucleus.This is why some particles bounced back.
Empty space
Solid nucleus
2. The nucleus has a positive charge, which is
why the positively charged alpha particles are
repelled if they get too close.
Empty space
Solid nucleus
Repelled by positively charged nucleus
If the nucleus has all the positive charge, then the
negatively charged electrons must be away
from the nucleus.
This is how we get Rutherford’s model of the
atom
Electron (negative charge)
Positive charge concentrated at the centre