Nuclear Energy Unit One Test

John Dalton
Thought up the Solid Sphere Model.  It could not be divided.

  • Located in the nucleus
  • Atomic mass of 1
  • Positive Charge


  • Located in circulation around the nucleus
  • Has almost no atomic mass
  • Negative Charge


  • Located in the nucleus
  • Atomic mass of 1
  • Nuetral charge (no charge)

Atomic Number
Number of protons in an atom
Atomic Mass

Mass of protons and neutrons



3 protons


7 neutrons


Atomic mass of  10

How do you use the periodic table?






1           <—-Atomic Number

H                        <—-Symbol

Hydrogen                         <—-Name

1.00794   <—-Average Atomic Mass


  • Different forms of an element
  • Different isotopes contain different numbers of neutrons

Average Atomic Mass
Average mass from a series of samples

Calculating Average Atomic Mass


Carbon 12:  98.9%

Carbon 14:  1.1%

98.9% * 12 / 100 = 11.868

1.1% * 14 / 100 = .154


11.868 + .154 = 12.022


Average Atomic Mass = 12.022amu

Ionizing Radiation

  • Radiation made up of particles (matter)
  • Alpha and Beta radiation

Electromagnetic Radiation

  • Radiation sent out in waves
  • Gamma radiation

Calculating Alpha (α) Decay



Pu240 94

  • Top number: Atomic Mass
  • Bottom Number: Atomic Number
  • Alpha decay causes atoms to lose 2 neutrons and 2 protons
  • Answer:

Pu240 94 —-α—-> U23692 + He42

Calculating Beta (β) Decay




  • Beta decay causes neutrons to lose their electron.
  • This leaves only the proton
  • Atomic Mass doesn’t change, but the Atomic number goes up


Po20984 —β—> At20985 + β0-1

Gamma Ray Radiation




  • No particles are disturbed during gamma ray radiation
  • There is only a loss of energy


Rn22286—γ—> Rn22286 + γ 00

Half Life

  • Amount of time it takes for 50% of a sample to decay into something else
  • Once half is gone, the remaining portion is cut by half, and so on
  • 1 –> ½ –> ¼ –> etc.

Link to see what half life looks like:

Nuclear Fission
The splitting of an atom
Chain Reaction

When a fast moving neutron hits an atom’s nucleus, the nucleus splits and releases 3

neutrons that in turn will hit the nuclei of 3 other atoms


Example Link:

Enriched Uranium

How much is needed in nuclear bombs? Power plants?

  • Uranium that is filtered to a specific amount of U-235 , the rare isotope
  • Bombs require at least 80% enriched uranium
  • Power Plants require 2-3% at most

Control Rods

  • Movable
  • Absorb neutrons released by fission
  • Slow down reaction


  • Absorb heat from reaction
  • Usually graphite
  • Slow down neutrons

Fuel Rods

  • Contain 2.5cm pellets of uranium
  • Spent nuclear fuel is a problem because it is still radioactive (emits α, β, and γ radiation)

Pros of Nuclear Power

Some examples:

  1. No greenhouse gases
  2. Needs very little uranium
  3. Large uranium deposits in Canada and Australia
  4. A single power plant creates huge amounts of energy

Cons of Nuclear Power

Some Answers:

  1. Radioactive Waste
  2. Not much uranium in the world
  3. Safety risks to the general public:
  4. Potential radiation exposure or explosion (melt down) if there is an accident

J. J. Thomson

  • Put magnets on either side of the Cathode Ray tube, found that the ray going through the tube was negatively charged (the ray curved towards the positive magnet)
  • Came up with the plum pudding / chocolate chip cookie model

Site for Cathode Ray Tube Diagram

Ernest Rutherford

  • Gold Foil Experiment (Shoots α particles at gold foil.  Most particles go through, some are repelled, others turn completely around)
  • Came up with nuclear and proton models of the atom

Gold Foil Experiment Diagram

Nuclear Model of the Atom

Proton Model of the Atom

Neils Bohr

  • Didn’t do many experiments, but had a problem with Rutherford’s nuclear model
  • Came up with a solution as to why electrons from nuclear model don’t crash into the nucleus: they have a set track!  High energy neutrons are further away from the nucleus, while low energy electrons are close to the nucleus

Solar System Model:

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