Conservation of nucleon number & charge
- Nuclear processes such as fission and fusion are represented using nuclear equations (similar to chemical reactions in chemistry)
- The number of protons and neutrons in atom is known as its constituents
- For example:
- The above equation represents a fission reaction in which a uranium nucleus is hit with a neutron and splits into two smaller nuclei – a Strontium nucleus and Xenon nucleus, releasing two neutrons in the process
- In nuclear equations, the nucleon number and charge are always conserved
- This means that:
- the sum of the nucleons on the left hand side must equal the sum of the nucleons on the right hand side
- the sum of the charge on the left hand side must equal the sum of the charge on the right hand side
- In the above equation, the sum of the nucleon (top) numbers on both sides are equal
- The same is true for the proton (bottom) numbers
- By balancing equations in this way, you can determine the nucleon number, proton number or the number of missing elements
- Let's consider another example:
- Determine the total nucleon number
- This is determined from the side of the equation where all the values are known
- In this example, from the reactants
-
- The total nucleon number = 235 + 1 = 236
- Equate the total nucleon number to the total nucleon number of the products including the unknown N
-
- Total nucleon number of reactants = 96 + 137 + (N ×1) = 236
- Rearrange to solve for N
- Balancing the equation shows that 3 neutrons must be released in the reaction
Worked example
When a californium atom reacts with an unknown element X, the following reaction occurs.
Determine the missing values of Y and Z.
Answer:
Step 1: Identify what the value of Y represents
- Y is the proton number of element X
Step 2: Determine the value of Y
- Determine the number of protons on both sides of the equation
Step 3: Identify what the value of Z represents
- Z is the nucleon number of the element Lr
Step 4: Determine the value of Z
- Determine the total nucleon numbers on both sides of the equation