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Nuclear Physics Cheat Sheet by

J.J Thompson's Model

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

Neils Bohr's model

Ruther­ford's model

Atomic Models

Matter infinitely divisible
Matter is made up of smaller parts, new matter is made up of small Lego like blocks of indivi­sable elements
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

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 are atoms with varying numbers of neutrons in the nucleus. The number of protons and electrons remain the same.


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

Half-Life Equations

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


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)
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.

Nuclear Fusion Equation

Theory of Special Relativity

Einsteins theory of special relativity (E=MC^2) allows us to calculate the energy released in a nuclear reactor

Radiation Badges



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