Chem (the alpha scattering experiment)

thousands of years ago, what did Ancient Greeks believe?

that everything was made from atoms and that atoms were tiny spheres that cannot be divided

what did scientists discover in 1897?

That atoms contain tiny negative particles called electrons

what did the discovery of electrons tell scientists

that atoms are not tiny spheres that cannot be divided

But instead have an internal structure

What was the new model that scientists suggested for the structure of atoms called?

The plum pudding modle

What’s an atoms in the plum pudding model

A ball of positive charge with negative electrons embedded in it

what did scientists want to know about the plum pudding model

If it was correct

What did scientists do to find out if the plum pudding model was correct

They carried out an experiment called the alpha scattering experiment

What is the alpha scattering experiment

One of the The most important experiments in science

why is the alpha scattering experiment important

because it radically changed the way we think about atoms

What’s the first step scientists did in the alpha scattering experiment

they took a piece of gold foil (because we can hammer gold into very thin foil)

What’s the second thing scientists did in the alpha scattering experiment ?

they fired tiny particles at the gold foil called alpha particles

What do alpha particles have?

a positive charge

What did scientists find out about alpha particles

That most of the alpha particles passed straight through the gold foil withought changing direction

What did the fact that most of the alpha particles went straight through the gold foil tell scientists?

that atoms are mainly empty space

Because the atoms in the plum pudding model were mostly empty space, what did this tell scientists?

that the plum pudding model was wrong

What did some of the alpha particles being deflected tell scientists?

that the centre of the atom must have a positive charge

What happens to any alpha particle that comes close to the positive centre of an atom?

It’s repelled and changes direction

What did some of the alpha particles bouncing straight back tell the scientists?

that the centre of an atom must contain a great deal of mass

What’s the central part of an atoms called

the nucleus

What did new experimental evidence lead to

the plum pudding model being replaced by the nuclear model