atomic structure Flashcards
what did the greek philosophers do
They believed hat tiny partcles of matter were so small they coudln’t be broken down into anything smaller
what did dalton do
proposed the atomic theory- that is all matter is made up of atoms and that all atoms are indivisible
who came after dalton
crookes
what did william crookes do
proved the existence of cathode rays
state and explain the experiemnt crookes did to prove the existence of cathode rays
Maltese cross experiemnt
What did William Crook’s experiment prove apart from the presence of cathode rays
He found that cathode rays travelling straight lines
What was the second experiment that William crooks conducted?
Paddle wheel experiment
In a vacuum at one end, he had an anode and at the other end a cathode
In between was a paddle wheel
Cathode rays moved towards the anode and as they did, they hit the puddle wheel causing it to turn
Define cathode rays
A stream of negatively charged electrons
What did William Crook’s paddle wheel experiment prove?
They have enough energy to move a paddle wheel
Who came after crookes experiment?
JJ Thompson
What did JJ Thompson discover?
He discovered the electron it’s minus charge and the charge to mass ratio of an electron
What experiment did JJ Thompson conduct first?
In a vacuum, he placed two parallel metal plates of opposite charge at halfway in the tube.
He had an anode and a cathode at one end, which were producing cathode rays that travel directly through the charge plates. When they hit the other side, they close the glass of Flores.
When the plate to return on the spot of glue move towards the positive plate indicating that they were negatively charged particle in the cathode rays
What was the second experiment that JJ Thompson did?
He placed a large electromagnet outside the glass tube and adjusted the strength of the magnetic field
He found out the electrons were also deflected in the magnetic field so he was able to bring the beam of electrons back down to its original position by adjusting the magnetic field
He use this to calculate the ratio of charge to mass of the electron
What was the charge to mass of the electron that JJ Thompson found?
E/M
What did JJ Thompson propose about the structure of an atom?
He proposed the plum pudding model
It is a sphere of positive charge and an electrons are embedded in the sphere of random
Who came after JJ Thompson?
Robert Millikan
What did Milliken discover?
He determine the size of the charge of the electron
What experiment did Milliken do to discover the charge of the electron?
The oil drop experiment
Explain Millikan oil drop experiment
He sprayed tiny droplets of oil between two charged metal plate plates
He used x-rays to ionise the air between the plates so the molecules in the air formed ions
As the oil droplets fell through the air, they picked up electrons and became negatively charged
He observed that the oil droplets were attracted to the positive plate
So we carefully adjusted the charge of the plate until the oil droplet was stationary and calculate the size of the charge of the electron by substitute on it into the charge to mass ratio that JJ Thompson had found
Who discovered the nucleus?
Rutherford
What experiment did Rutherford do to discover the nucleus?
He did a gold foil experiment
Explain Rutherford’s gold foil experiment
He he bombarded a thin piece of gold foil with the alpha particles which are positively charged.
He placed a screen of Zilke zinc sulphate which would light up if hit by an alpha particle behind the gold foil
Rutherford found that some alpha particles were deflected at large angles some deflected back along their path and some went straight through
He concluded that the positive charge and the mass of the atom of the metal foil was concentrated in a small dense core called the nucleus
He concluded this as very few were reflected back along their own path, some were deflected out wide angles and most went straight through
What did Rutherford’s observation conclude?
That most of the atom is empty space as most particles went straight through
The alpha particles are repelled when they pass the small positive nucleus as some more deflected at large angles
A small number of alpha particles collided head on with the nucleus indicating the nucleus is very very tiny so most of the atom is empty. Space
Who discovered the proton?
Rutherford also discovered the proton as well as the nucleus
