Question

which of these is a fusion reaction (A) \({ }^{3}{ }_{1} \mathrm{H}+{ }_{1}^{2} \mathrm{H}={ }_{2}^{4} \mathrm{He}+{ }_{0} \mathrm{n}^{1}\) (B) \({ }^{12}{ }_{7} \mathrm{C} \rightarrow{ }_{6} \mathrm{C}^{12}+\beta^{+}+\mathrm{g}\) (C) \({ }_{92} \mathrm{U}^{238} \rightarrow{ }^{206}{ }_{82} \mathrm{~Pb}+8\left({ }_{2}^{4} \mathrm{He}\right)+6\left(_{1-} \mathrm{e}\right)\) (D) None of these

Short answer

The correct answer is (A) \({ }^{3}{ }_{1} \mathrm{H}+{ }_{1}^{2} \mathrm{H}={ }_{2}^{4}\mathrm{He}+{ }_{0} \mathrm{n}^{1}\) as this is a fusion reaction involving the combination of tritium and deuterium nuclei to form a heavier helium-4 nucleus and a neutron.

Step-by-step solution

Analyze each reaction type

Let's analyze each given reaction to determine if it is a fusion reaction. (A) \({ }^{3}{ }_{1} \mathrm{H}+{ }_{1}^{2} \mathrm{H}={ }_{2}^{4}\mathrm{He}+{ }_{0} \mathrm{n}^{1}\) Here, we have two atomic nuclei, tritium (\({ }^{3}{ }_{1} \mathrm{H}\)) and deuterium (\({ }_{1}^{2} \mathrm{H}\)), combining to form a single heavier nucleus, helium-4 (\({ }_{2}^{4}\mathrm{He}\)), and a neutron. This seems like a fusion reaction. (B) \({ }^{12}{ }_{7} \mathrm{C} \rightarrow{ }_{6}\mathrm{C}^{12}+\beta^{+}+\mathrm{g}\) In this reaction, one nucleus, carbon with a mass number of 12 and an atomic number of 7 (\({ }^{12}{ }_{7} \mathrm{C}\)), is decaying into another nucleus, carbon with a mass number of 12 and an atomic number of 6 (\({ }_{6}\mathrm{C}^{12}\)), while also emitting a positron (\(\beta^{+}\)) and a photon (g). This type of reaction is not fusion, as there's no combining of atomic nuclei. (C) \({ }_{92} \mathrm{U}^{238} \rightarrow{ }^{206}{ }_{82}\mathrm{~Pb}+8\left({ }_{2}^{4} \mathrm{He}\right)+6\left(_{1-}\mathrm{e}\right)\) In this reaction, a uranium-238 nucleus (\({ }_{92} \mathrm{U}^{238}\)) is breaking apart into a lead-206 nucleus (\({ }^{206}{ }_{82}\mathrm{~Pb}\)), eight helium-4 nuclei, and six electrons. This is a fission reaction, not fusion, as the initial nucleus is splitting into smaller ones.

Determine the correct answer

Now that we analyzed each reaction, we can confidently say that the correct answer is: (A) \({ }^{3}{ }_{1} \mathrm{H}+{ }_{1}^{2} \mathrm{H}={ }_{2}^{4}\mathrm{He}+{ }_{0} \mathrm{n}^{1}\) This is a fusion reaction because two atomic nuclei, tritium and deuterium, combine to form a single heavier nucleus, helium-4, and a neutron.

Key concepts

Nuclear Fusion

Nuclear fusion is a process where two light atomic nuclei come together to form a heavier nucleus. It is the same reaction that powers the sun and other stars, converting hydrogen into helium. In these fusion reactions, some of the mass of the hydrogen nuclei is converted into energy, according to Einstein’s equation, \( E = mc^2 \).
Fusion requires extremely high temperatures and pressures to overcome the electrostatic forces that normally keep nuclei apart. This environment allows nuclei to come close enough for the strong nuclear force, which is attractive and operates at very small distances, to bind them together.
The main benefits of nuclear fusion include its potential as a clean and virtually limitless source of energy, as it produces minimal radioactive waste compared to fission. However, achieving and sustaining the conditions necessary for fusion on Earth is technologically challenging. Ongoing research seeks to make fusion a viable energy source in the future.

Tritium and Deuterium Reaction

The tritium and deuterium reaction is a classic example of nuclear fusion. Tritium ( ^{3}_{1}H ) and deuterium ( ^{2}_{1}H ) are both isotopes of hydrogen. In the reaction, these two isotopes combine to form a heavier helium-4 nucleus ( ^{4}_{2}He ), releasing a neutron ( ^{1}_{0}n ) in the process.
This reaction is significant because it releases a substantial amount of energy, more than some other fusion reactions. Importantly, it requires somewhat lower temperatures and pressures than other fusion processes, such as those involving pure hydrogen, making it more feasible for experimental fusion reactors.
The tritium and deuterium reaction is also central to research on controlled nuclear fusion for energy production. Tritium is radioactive, while deuterium is stable and naturally more abundant; however, tritium can be bred in reactors, making this fusion pathway an attractive target for achieving practical fusion energy.

Alpha Particle Production

Alpha particle production is an essential component of the tritium and deuterium fusion reaction. In this context, an alpha particle is simply a helium-4 nucleus ( ^{4}_{2}He ), composed of two protons and two neutrons.
When tritium and deuterium undergo fusion, they produce an alpha particle, which carries part of the energy released in the reaction. This energy can be harnessed for power generation by converting the kinetic energy of the alpha particle into electricity.
Understanding alpha particle production is crucial because these particles can affect the stability and efficiency of a fusion reactor. The alpha particles transfer energy to other reactants within the reactor, which helps maintain the necessary temperature to sustain continuous fusion. Controlling the behavior of alpha particles is thus a key aspect of designing efficient fusion reactors.