ATOM Flashcards
John Dalton 1800
Tiny spheres that could not be divided
Jj Thompson 1890
Electron discovered.
Plum pudding model - spheres of positive charge with negative charges spread evenly through
E.Rutherford, Geiger and Marsden 1908-1913
Alpha particle scattering experiment.
Nuclear model - mass of atom concentrated in a charged nucleus, with orbiting electrons
Niels Bohr 1914
Electrons orbit nucleus at specific distances in fixed energy levels (shells). Energy given out when electrons change level
Later
Positive charge of nucleus could be subdivided into particles of positive charge - protons
James Chadwick 1932
Provided evidence for the existence of neutrons within the nucleus
Mass of a proton
1
Mass of a neutron
1
Mass of an electron
Very small
Charge of a proton
+1
Charge of a neutron
0
Charge of an electron
-1
Location of a proton
Nucleus
Location of a neutron
Nucleus
Locations of electrons
Shells
Where’s most of the mass found in an atom
The nucleus
Number of protons =
Atomic number
Atomic number =
Number of protons
Why do atoms have no overall electrical charge?
Because the number of positive protons equals the number of negative electrons
Mass number =
Number of protons and neutrons
Number of protons and neutrons =
Mass number
Number of protons =
Atomic number
Atomic number =
Number of protons
Mass number - atomic number =
Number of neutrons
Number of neutrons =
Mass number - atomic number
