Question 10.6: Write a nuclear equation for the fission of uranium-235 by n...
Write a nuclear equation for the fission of uranium-235 by neutron bombardment to form strontium-90, an isotope of xenon, and three neutrons.
Analysis
Balance the atomic numbers and mass numbers on both sides of the nuclear equation. In fission reactions, include the neutron used for bombardment on the left and the high-energy neutrons produced on the right. Each neutron has a mass of one and zero charge.
[1] Write an incomplete equation with the original nucleus and neutron used for bombardment on the left, and the particles formed on the right.
• Use the identity of each element to determine its atomic number. Uranium has an atomic number of 92, and xenon has an atomic number of 54.
• Include one neutron on the left side. In this reaction, three high-energy neutrons are formed, so include three neutrons on the right side.
{ }_{92}^{235} \mathrm{U}+{ }_0^1 \mathrm{n} \longrightarrow{ }_{38}^{90} \mathrm{Sr}+{ }_{54}^? \mathrm{Xe}+3{ }_0^1 \mathrm{n}
[2] Calculate the mass numbers and atomic numbers of all newly formed nuclei on the right.
• Atomic number: In this problem all atomic numbers are known from the identity of the elements.
• Mass number: Balance mass numbers by taking into account the mass of the neutrons used or produced in the reaction. On the left side, the total mass of the particles (the uranium nucleus and one neutron) is 236 (235 + 1). On the right side, the sum of the masses of Sr-90, xenon, and three neutrons (total mass of three) must also equal 236
[3] Write the complete equation.
{ }_{92}^{235} \mathrm{U}+{ }_0^1 \mathrm{n} \longrightarrow{ }_{38}^{90} \mathrm{Sr}+{ }_{54}^{143} \mathrm{Xe}+3{ }_0^1 \mathrm{n}