7.2 Alpha Particle Scattering Flashcards
What did JJ Thomson suggesr?
That atoms were spheres of positive charge with tiny negative electrons stuck in them.
What was the name of the model JJ Thomson suggested?
The plum pudding model
Who disproved the plum pudding model?
Ernest Rutherford.
What is the alpha particle scattering experiment?
A stream of alpha particles from a radioactive source were fired at a thin sheet of gold. Using a fluorescent screen their position after meeting the sheet would be recorded, as alpha particle would create flashes upon touching the screen.
Why was it gold?
They used gold in this experiment since it was the most malleable,this meant the thinnest sheet could be mad3e out of this material.
Why did the sheet of gold need to be thin?
A sheet of too great of a thickness could stop the transmission through it.
Why did we have to remove the air in this experiment?
To avoid alpha particles interacting with the air particles, thus effecting the results of the experiment.
What happened to most alpha particles in this experiment? What was the conclusion due to this?
They went straight through the sheet , undeflected.
This suggested that most of the space of the atom is empty.
What happened to some alpha particles? What was the conclusion due to this?
Some alpha particles were deflected across small angles.
This suggested there must be a large positive charge in the centre where a particles would be deflected entering the nucleus’ electric field.
What happens to the energy stored in alpha particles as they enter the electric field of the nucleus?
The kinetic energy would be changed to electric potential when entering and regain Ek when repelled.
What happened to a very small number of alpha particles? What is the conclusion for this?
A few were reflected straight back by an angle of 90 degrees or greater.
Sugggesting that there is a concentrated mass in the middle - since alpha particles can only be deflected by something a lot more massive then them
What would happen in the alpha scattering experiment if the plum pudding model was correct?
All flashes would have been seen within a small angle of the stream of the alpha particles on the fluorescent screen.
Where is the force on the alpha particle at its strongest and why?
Closest to the nucleus. This is because of the equation F = kQQ/r^2. This is an inverse square law where force increases as distance decreases.
What happens when an alpha particle gains an electron?
It starts to behave like helium gas, emitting a spectrum.
What is the process called when all energy is regained back to original energy store (e.g. when an alpha particle interacts with the nucleus it loses and regains Ek)
Elastic interaction
