Chapter 1.5 History of the atom Flashcards
Which scientists proposed key ideas successfully about the model of them atom?
Dalton, Thomson, Rutherford, and Bohr.
Who discovered the electron?
J.J. Thomson.
How did J.J. Thompson provide evidence for the electron?
In the second experiment, he discovered that the charge in the cathode rays(streams of electrons observed in vacuum tubes) were negative. He deduced that the cathode rays were made up of negatively-charged particles.
What was the evidence for the nucleus?
Very occasionally an alpha particle bounced back in the direction it came from. This lead to the conclusion that an atom had a small, dense positively charged nucleus at its centre and that most of the rest of an atom was empty space.
What was the evidence for the electrons in shells?
Bohr proposed that electrons are restricted to certain fixed orbits. An electron can jump, suddenly, between these orbits by absorbing a photon.
How did Chadwick provide evidence for neutrons in the nucleus?
Chadwick measured the range of these protons, and also measured how the new radiation impacted the atoms of various gases. He found that the new radiation consisted of not gamma rays, but uncharged particles with about the same mass as the proton. These particles were neutrons.
