Problem 58 - Chemistry and Chemical Reactivity

Question

Tritium, \(_{1}^{3} \mathrm{H},\) is one of the nuclei used in fusion reactions. This isotope is radioactive, with a halflife of 12.3 years. Like carbon- \(14,\) tritium is formed in the upper atmosphere from cosmic radiation, and it is found in trace amounts on Earth. To obtain the amounts required for a fusion reaction, however, it must be made via a nuclear reaction. The reaction of \(_{3}^{6}\) Li with a neutron produces tritium and an \(\alpha\) particle. Write an equation for this nuclear reaction.

Step-by-Step Solution

Answer

\(_{3}^{6}\text{Li} + _{0}^{1}\text{n} \rightarrow _{1}^{3}\text{H} + _{2}^{4}\text{He}\).

Step 1: Identify the Reactants

The problem states that the reaction involves lithium-6 (\(_{3}^{6}\text{Li}\)) and a neutron (\(_{0}^{1}\text{n}\)) as the reactants. These are the particles that will interact in the nuclear reaction.

Step 2: Recognize the Products

The reaction produces tritium (\(_{1}^{3}\text{H}\)) and an \(\alpha\) particle. An \(\alpha\) particle is a helium nucleus, which is represented as \(_{2}^{4}\text{He}\).

Step 3: Write the Nuclear Reaction Equation

To write the equation, balance the atomic numbers and mass numbers on both sides of the equation. The equation for the reaction is:\[_{3}^{6}\text{Li} + _{0}^{1}\text{n} \rightarrow _{1}^{3}\text{H} + _{2}^{4}\text{He}\]Check that the mass number (top number) and atomic number (bottom number) are balanced both before and after the reaction. Here, both are balanced:- Mass numbers: \(6 + 1 = 7\) and \(3 + 4 = 7\)- Atomic numbers: \(3 + 0 = 3\) and \(1 + 2 = 3\)

Key Concepts

Tritium Production

Tritium, also known as hydrogen-3, is a radioactive isotope of hydrogen. It does not occur abundantly on Earth and needs to be produced in labs or reactors for practical use. Tritium is primarily produced by the nuclear reaction between lithium-6 and a neutron. This interaction results in the formation of tritium and an alpha particle, which is a helium nucleus.

• Reactants: In this reaction, the reactants are lithium-6 (_{3}^{6} ext{Li}) and a neutron (_{0}^{1} ext{n}).
• Products: The products formed are tritium (_{1}^{3} ext{H}) and an alpha particle (_{2}^{4} ext{He}).

The balanced nuclear equation for this tritium-producing reaction is:\[_{3}^{6} ext{Li} + _{0}^{1} ext{n} \rightarrow _{1}^{3} ext{H} + _{2}^{4} ext{He}\]This equation ensures that the sum of atomic numbers and mass numbers are equal on both sides, conserving both kinds of charges. Tritium is then collected for use mostly in nuclear energy applications, like fusion reactions.

Radioactive Isotopes

Radioactive isotopes, or radioisotopes, are atoms that have unstable nuclei. They will eventually transform into a different atom by releasing nuclear energy in the form of radiation. Tritium is a perfect example, being a radioactive isotope of hydrogen with a half-life of 12.3 years.

• Decay Process: Tritium decays by a process called beta decay. During this process, a neutron converts into a proton, and the isotope changes from tritium to helium-3 ( _{2}^{3} ext{He} ), releasing an electron (beta particle) and an anti-neutrino.
• Half-life: The half-life of a radioactive isotope is the time required for half of the radioactive atoms in a sample to decay. For tritium, this is 12.3 years, meaning every 12.3 years, half of the tritium atoms will have decayed into helium-3.

These properties make radioactive isotopes useful in various fields like medicine, where radioactive tracers are used for diagnostic purposes, or in energy, where they can sustain chain reactions in nuclear reactors. However, handling and disposal require careful management due to the radiation they emit.

Fusion Reactions

Fusion reactions involve the combining of lighter atomic nuclei to form a heavier nucleus, with the release of a substantial amount of energy. These reactions are what power the sun and other stars, providing an enormous source of energy. Fusion reactions hold potential for cleaner and safer energy production compared to fission.

• Fusion Fuel: Tritium is one of the key materials used in fusion reactions, often paired with deuterium (another hydrogen isotope) to form helium and release energy. The fusion of these isotopes occurs at extremely high temperatures and pressures, like those found in stars.
• Energy Output: The energy produced in fusion reactions is due to the conversion of mass to energy, as described by Einstein's equation \( E=mc^2 \). This means a very small amount of matter is transformed into a large amount of energy.

Realizing nuclear fusion as a practical energy source on Earth involves replicating these extreme conditions in a controlled manner, such as using magnetic confinement in tokamaks or inertial confinement techniques. Tritium, with its ability to release neutrons during fusion, is integral to the success of such initiatives, helping to sustain and promote the fusion process.