Rutherford's Gold Foil Experiment Explained
In Rutherford's gold foil experiment an Alpha particle emitter is placed inside a vacuum chamber pointing at a leaf of gold foil. Around the gold foil is a circular sheet of Zinc Sulfide (ZnS). The Zinc Sulfide emits Photons (light) when it absorbs Alpha particles. |
If Thompson's model of the atom was correct then the Alpha particles would have passed through largely unaffected with possibly some slight deflection |
But when Rutherford ran his experiment 98% passed straight through, just under 2% deflected at a large angle and less than 1% were reflected straight back at the emitter. |
Rutherford's Gold Foil Experiment
Atomic Models
Aristotle |
Matter infinitely divisible |
Democratis |
Matter is made up of smaller parts, new matter is made up of small Lego like blocks of indivisable elements |
Dalton |
Matter is divisible to the extreme but not infinitely divisible. |
J.J. Thompson |
Uniformly spaced electrons in positively charged cloud of matter |
Ernest Rutherford |
Most of the atom is empty space with a dense nucleus. |
Neils Bohr |
Electrons exist in discrete and fixed energy shells surrounding the nucleus |
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Types of Radiation
Alpha particles |
Helium nuclei, highly charged (+2), heavy, slow, travels few cm in air, stopped by a sheet of paper |
Beta particles |
Electron, -1 charge, light (1/1836 atomic mass), fast (90% light speed), stopped by 5mm of metal, travels 30cm in air |
Gamma Rays |
Electromagnetic radiation, shortwave length, high frequency, travels at lightspeed, can penetrate several cm of lead |
Isotopes
Isotopes are atoms with varying numbers of neutrons in the nucleus. The number of protons and electrons remain the same. |
Half-Life
The Half-Life of a radioactive isotope is the length of time it takes for the number of atoms of that isotope to have decreased by half, this does not mean half the mass or volume |
Nuclear Equation Rules
Mass number must be equal on both sides of the equation |
Charge must be equal on both sides of the equation |
Nuclear Fission
Fission is what happens when a large unstable nucleus absorbs a neutron, then splits in half |
Uranium 235 fission equation
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Nuclear Fission Reactor
Fuel Rods |
Fuel rods are usually Uranium 238 enriched with 3% Uranium 235 |
Control Rods |
Control rods are used to control the fission rate (usually made of Silver, Iridium, Cobalt, Cadmium or Boron) |
Coolant |
The Coolant carries energy to the steam generator. (Can be any liquid but usually Water or molten metal |
Nuclear Reactor Diagram (Fission)
Nuclear Fusion
Nuclear Fusion is when two small nuclei fuse to form a larger nucleus. |
Theory of Special Relativity
Einsteins theory of special relativity (E=MC^2) allows us to calculate the energy released in a nuclear reactor |
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