What do the red balls represent?
protons
Helium has 2 protons and 2 neutrons. The neutrons are green, so the protons must be red.
What are deuterium and tritium?
Isotopes of hydrogen
They each contain one proton, so they are hydrogen.
What is the clump of 3 green circles and 2 red circles?
This is an isotope of helium (it has 2 protons), called He-5, because it has 5 total nucleons.
What is the difference between the small circles and the larger circles?
The small circles are nucleons: protons and neutrons. The large circles represent the atomic nucleus because they have too many nucleons to draw each one.
What does U-235 and U-236 mean?
These are isotopes of uranium. The numbers represent the number of nucleons in the nucleus or its atomic mass. U-236 has one more neutron than U-235. The diagram is showing the neutron being added to a U-235 nucleus to create U-236.
What are Ba-144 and Kr-89?
Barium-144 and Krypton-89
What is the significance of the three neutrons produced in the reaction?
If there were no neutrons produced, there would be no chain reaction.
If there were only one neutron produced, then the chain reaction would eventually fail when the neutron did not hit the next nucleus.
Three neutrons not only increases the chance that the chain reaction will continue, but provides the possibility for the chain reaction to grow in an explosive manner.
What products of nuclear fission are not shown?
Gamma rays
What is the form of energy that is released in nuclear fission?
Most of the energy is in the kinetic energy of the daughter nuclei.
Some energy is in the kinetic energy of the neutrons and some in the gamma rays.
The kinetic energy of the particles is quickly converted into heat as they strike other atoms.
What is the critical mass?
The critical mass is the amount of matter needed to create a sustained fission reaction. The reaction becomes sustained when enough neutrons interact with new uranium nuclei rather than leaving the mass.
How is the relationship between volume and surface area important in the concept of critical mass?
The volume increases in proportion to the cube of the radius of the mass, while the surface area only increases by the square of the radius.
Therefore, the volume increases faster than the surface area. So, as the mass increases, the number of neutrons produced increases faster than the number of neutrons being lost out of the mass, until at the critical mass, there are enough neutrons to sustain the reaction.
Where do these reactions occur?
Nuclear fission occurs in atomic bombs and nuclear reactors.
Nuclear fusion occurs in the sun and in hydrogen bombs. Attempts are being made to create a fusion reactor.
Is fusion a chain reaction?
No. The neutron produced is not used in a new reaction.
CoMo Science 
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