2. Atomic structure Flashcards
Who proposed an atomic theory in 1808?
John Dalton; Dalton’s Atomic Theory
- All matter is made up of minute particles
- All atoms are indivisible ie they cannot be broken down into simpler particles
Who studied the discharge of electricity through gases in 1875?
William Crookes: Maltese Cross Tube - the shadow of the Maltese cross on the opposite side of the tube showed that radiation was coming from the cathode in the form of Cathode rays.
Paddle Wheel Tube: the cathode rays had enough energy to turn the paddle wheel
Who discovered that cathode rays were negative in 1897?
J.J Thomson
Who suggested the name electrons ?
George Stoney
Who calculated the charge of electrons (e) and their mass (m) in 1909?
Robert Millikan ; oil drop experiment
Who discovered the nucleus and proton in 1909?
Ernest Rutherford ; gold foil experiment
Who discovered the neutron in 1932 and how?
James Chadwick ; bombarded beryllium nuclei w alpha particles. Small neutral particles released.
Def. Cathode rays
Cathode rays are streams of electrons. They are negatively charged and have enough energy to move a paddle wheel.
They move in straight lines from the cathode to the anode and can be deflected by electric and magnetic fields.
What is the relative mass of an electron?
1/1838
What did the Greeks believe about atoms?
All matter is made up of small, indivisible particles.
What proof is there for the existence of atoms?
The process of diffusion .
