IB Chemistry nuclear fusion and fission explained
IB Chemistry is known for being a challenging subject, so we’ve pulled some useful explanations of key concepts from our study guides to help make your revision a bit easier. If you’re studying IB Chemistry Option C: Energy then this straightforward explanation of nuclear fusion and nuclear fission extracted from our IB study guide, Chemistry Option C: Energy Standard and Higher Level written by Tony Hickling, is for you. The study guide is full of concise, easy-to-understand explanations of complicated concepts that can help you stay on top of your IB Chemistry Option C studies. The guide also contains over 25 practice questions plus four exam-style questions to allow you to test your knowledge and understanding.
Nuclear fusion and fission
Nuclear energy is energy that is released when atomic nuclei change. There are two ways this can happen: nuclear fusion and nuclear fission.
Nuclear Fusion
Nuclear fusion occurs when two very light nuclei (such as hydrogen) combine together to make a larger nucleus.
Enormous heat and pressure are required to overcome the electrical repulsion of protons but there is a net release of energy in the process.
Example equation:
In the example above, the symbols represent the nuclei of hydrogen. They combine to make a helium nucleus, a helium-3 isotope in this example. Some of the energy produced is carried away as gamma ray photons.
The lower number to the left of each symbol is the atmoic number and is the same as the number of protons. This represents the relative charge of the nucleus. Charge is conserved so that 1 + 1 = 2 on the bottom line of the equation.
The upper number is the mass number. It is the sum of the protons + neutrons. Mass is also conserved so that 1 + 2 = 3.
Nuclear Fission
Nuclear fission occurs when a very heavy nucleus (such as uranium or plutonium) splits into medium sized nuclei.
In addition to releasing energy this process also releases neutrons, some of which might be absorbed by other heavy nuclei to produce more fission! Only a few heavy nuclei are ‘fissionable’ in this way and the fission products are varied.
Example equation:
is the symbol for a neutron. You will again see that both charge and mass are conserved.
Mass (the top line): 235 + 1 = 236 = 144 + 89 + 3
Charge (the bottom line): 92 + 0 = 92 = 56 + 36 + 0
In your exam you might be set problems ‘balancing’ these nuclear equations. You do not need to learn any specific nuclear equations but you do need to be able to deduce mass numbers and atomic numbers or the name of the elements for the nuclei involved, if given enough information.
Expanding your IB Chemistry Option C: Energy knowledge
This quick review of nuclear fusion and fission has hopefully helped to reinforce your understanding. If you’re looking for practice questions on this topic or more succinct explanations of key concepts in IB Chemistry Option C, then pick up a copy of our study guide. A table of contents for the book as well as some sample pages are available through the link below. If you’re looking for more help with IB Chemistry, including hints for your IA, then be sure to visit our Chemistry subject page where you’ll find more articles, study tools, and other resources.
