Download Evolution of the Atomic Theory

Evolution of the Atomic
Theory
Visualizing the ATOM
Another Addition
• 1911 – Ernest Rutherford
• Gold Foil Experiment
• Bombarded a piece of gold foil with alpha particles
(positively charged particles).
The Experiment Setup
The Experiment Results
Rutherford’s Experiment
• Gold Foil Experiment
• Observations:
• 1. a large majority of alpha particles passed directly through the foil.
• 2. few particles were deflected when shot at the foil.
• 3. rarely, one particle would come back almost directly at the alpha source
More progress! The Atomic Model
• Conclusions:
• 1. Most of an atom consists of empty space.
• 2. There lies a condensed positive mass in an element.
• Rutherford discovered the positively charged
atomic nucleus.
Rutherford’s Atomic Model
Discovery of the Proton
• Although Rutherford was credited with the positive nucleus, Eugene
Goldstein was credited with the discovery of protons.
• “Anode beam” – similar to Thomson
Up to this point in time…
• Mass ratio tests were experimented on these
subatomic particles to tell us:
Subatomic
Particle
Electric
Charge
Actual Mass
Relative
Mass
(amu)
Electron
-1
9.11 x 10-31 kg
0
Proton
+1
1.67 x 10-27 kg
1
The Last Addition
• 1932 – James Chadwick
• There had to be something else!!
• 1. This particle had to be electrically neutral.
• 2. This particle had to contribute to the atoms mass.
• Chadwick would later name this mystery particle
the neutron; which is located in the nucleus of an
atom.
Chadwick’s Contribution
Subatomic Particles:
Subatomic
Particle
Electric
Charge
Actual Mass
Relative
Mass
(amu)
Electron
-1
9.11 x 10-31 kg
0
Proton
+1
1.67 x 10-27 kg
1
Neutron
0
1.67 x 10-27 kg
1