development of the atom Flashcards
what was J.J Thompson’s experiment
he placed 2 oppositely charged electric plates around a cathode ray. the cathode ray deflected away from the negative plate towards the positive plate
what did his experiment show
it showed the cathode ray has negative particles
what else did Thompson do
he placed 2 magnets on either side of the tube and observed this magnetic field also deflected the cathode ray
what did using the magnets help determine
it helped determine the mass to charge ratio of cathode ray particles and showed the mass of the negative particle was much smaller than any atom
what did Thompson discover when he repeated the experiment
he repeated the experimetn using different metals as electrodes materials and found properties of cathode ray remained constant no matter what the material was.
what were the overall conclusions of the cathode ray experiment
the cathode ray is composed of negative particles which he called the electron
this must exist as part of the atom
subatomic particles are found within all atoms of all elements
what was Thompsons model called
the plum pudding model which showed the atom as being a ball of positive charge with negative electrons embedded in it
what was Ernest Rutherford’s experiment called
the alpha scattering experiment
what did the alpha scattering experiment consist of
it was a setup consisting of alpha particles being fired at thin gold foil and a detector on the other side to detect how many particles deflected at different angles
what were the results of the ASE
alpha particles are positively charged, when fired at thin gold foil, most of them go straight through but a small number bounced straight back
what were the conclusions of the ASE
majority of the particles went straight through
- suggested atom is mainly empty space
some particles deflected through small angles of 10 degrees
- positive nucleus at the centre
only a small number of alpha particles deflected straight back at angles of 90 degrees
- nucleus is extremely small where the mass and charge of an atom is concentrated
what did rutherford determine about the structure of the atom
atoms consist of small dense positively charged nuclei. since atoms were thought to be neutral, negative electrons were thought to be on a positive sphere of charge. these electrons now orbit the nucleus collectively making up the atom
what did henry mosely do
he used xray spectroscopy to establish mathematical study between atomic number of elements and the wavelength of the xrays
what did Henry Mosely’s work do
his work redefined atomic numbers, into a value that can be used to order the elements in the periodic table.
what did Mosely’s work support
it supported the concept of atomic structure put forward by Ernest Rutherford which has compact positively charged nucleus surrounded by orbiting cloud of electrons. his work also understood atomic number to be the exact number of positive charges in the nucleus of an atom
