1. Fundamental Particles of Matter
Electrons
Cathode Ray Tube Experiments
Millikan oil-drop experiment
Davy, Faraday, Stoney, Thomson
Protons
Rutheford scattering experiment
Neutrons
-Bombardment experiments
Chadwick

2. Cathode rays
Travel in straight lines
Negatively charged
Have mass
Cathode rays = Electron beam
Thomson determined the e/m ratio by studying the deflection of the beam in electric and magnetic fields

3. Millikan Drop analysis
Determined the charge (e) on an electron from the experiment
e/m = *108 C/g from the cathode ray exp.
m = *108 C/g * e = *10-28 g

4. Canal Rays = Positive (cation) rays
Original “Plum
Pudding” Model
Protons
Cathode Ray Tube Experiments
Atom  cation+ + e-
Canal Rays = Positive (cation) rays
H2  2H+ + 2e-
Determined the e/m of a proton
Rutheford Scattering Experiment
Nucleus
New
Model

5. An atom is defined by the # of protons
Atomic Number
Moseley
Bombarded Elements with high energy e-
Produced different wavelengths for different element
Each element differs from the preceding element by having one more proton
An atom is defined by the # of protons

7. Isotopes - Atoms of the same element (have the same # of protons) that have different masses (have differing number of neutrons)
Mass number A = Z (#p) + #n
Nuclide Symbol E A Z 10 5 11 5 B
#n=5 B
#n=6

8. Mass Spectrometry - measures the charge-to-mass (e/m) ratio of
Mass Spectrometry - measures the charge-to-mass (e/m) ratio of charged particles.
If we put Neon in a mass spectrometer we could determine how many
natural isotopes there are for neon and the percent abundance of each
isotope
20Ne %
21Ne %
22Ne %
atomic mass of
Ne = * * *0.925
atomic mass Ne = amu