Question

Which isotope of hydrogen is radioactive? Write the nuclear equation for the radioactive decay of this isotope.

Short answer

The radioactive isotope of hydrogen is tritium (³H), which undergoes beta decay. The nuclear equation for its radioactive decay is: \[ {}^3_1H \rightarrow {}^3_2He + {}^0_{-1}\beta \]

Step-by-step solution

Identify the radioactive isotope of hydrogen

Among the three isotopes of hydrogen, protium (¹H) has 1 proton and no neutrons, deuterium (²H) has 1 proton and 1 neutron, and tritium (³H) has 1 proton and 2 neutrons. Out of these, tritium is radioactive due to its unstable nucleus, which undergoes beta decay over time.

Determine the type of radioactive decay tritium undergoes

Tritium, being a radioactive isotope, undergoes beta decay. In beta decay, a neutron in the nucleus is converted into a proton, and an electron (called beta particle) is emitted. The emission of this beta particle helps make the nucleus more stable.

Write the nuclear equation for tritium's decay

To write the nuclear equation for the radioactive decay of tritium, we need to show the initial tritium nucleus, the emitted beta particle, and the resulting nucleus after decay. Since tritium has 1 proton and 2 neutrons, it is represented by the symbol ³H. During beta decay, a neutron converts to a proton, and the atom changes to a helium isotope, which has 2 protons and 1 neutron (³He). The nuclear equation for tritium's beta decay is: \[ {}^3_1H \rightarrow {}^3_2He + {}^0_{-1}\beta \] In this equation, ³H decays into ³He, with the emission of a beta particle (notated by \({}^0_{-1}\beta\)). The numbers on the top and bottom of each symbol represent the mass number (number of protons + neutrons) and atomic number (number of protons) respectively. Note that the mass numbers on each side of the equation are equal (3), and the atomic numbers also balance out (1 on the left, and 1-1=0 on the right).

Key concepts

Hydrogen Isotopes

Hydrogen, the most abundant element in the universe, has three isotopes that are distinct from one another based on their atomic composition. These isotopes are protium (¹H), deuterium (²H), and tritium (³H). Each isotope has a different number of neutrons in the nucleus, while all share the same number of protons (one proton). This small change in neutron count significantly impacts the stability and radioactivity of each isotope.

• Protium (¹H): Contains one proton and no neutrons. It is stable and by far the most common hydrogen isotope.


• Deuterium (²H): Known as heavy hydrogen, it has one proton and one neutron. Deuterium is stable and is used in various scientific and industrial applications.


• Tritium (³H): This isotope has one proton and two neutrons. Unlike the other two, tritium is radioactive due to the instability brought on by its additional neutron.

Understanding these differences helps identify which forms of hydrogen can contribute to or are involved in nuclear reactions, such as tritium's significance in nuclear chemistry.

Nuclear Equations

Nuclear equations are like chemical equations but for nuclear reactions or transformations. They describe what happens when an atomic nucleus changes, often emitting or capturing particles. These equations must balance in terms of the total number of nucleons (protons and neutrons) and charge. Here's how nuclear equations work:

• Components: The equation includes the initial nucleus, any resulting nuclei, and any particles emitted or captured.


• Balancing: The sum of the mass numbers (total protons and neutrons) and atomic numbers (protons) must be the same on both sides of the equation.

For example, the decay of tritium (³H) into helium-3 (³He) through beta decay can be written as:\[ {}^3_1H \rightarrow {}^3_2He + {}^0_{-1}\beta \]In this equation, the tritium loses a neutron, becomes more stable, and emits a beta particle. The equation accurately reflects the conservation of mass and charge during the process.

Beta Decay

Beta decay is a type of radioactive decay where a neutron in the nucleus converts into a proton, along with the emission of an electron, known as a beta particle. This process occurs in isotopes with a neutron-to-proton ratio that creates instability, such as tritium. Here's how beta decay operates:

• Transformation: A neutron is transformed into a proton, thereby increasing the proton count by one. This results in a shift in the element on the periodic table, as the atomic number grows.


• Particle Emission: Alongside the new proton, an electron (the beta particle) and an antineutrino are emitted. The beta particle is a high-energy electron originating from the nucleus.

Beta decay helps unstable isotopes reach a more stable state. In the case of tritium, it turns into helium-3, with only a slight mass change but significant stability improvement.

Nuclear Chemistry

Nuclear chemistry is a branch of chemistry focusing on the reactions and properties of atomic nuclei. It explores phenomena like radioactivity, nuclear decay processes, and reactions within the nucleus. Here are key highlights of nuclear chemistry:

• Radioactivity: The emission of particles and energy from atomic nuclei. This can occur naturally or be induced in laboratories.


• Nuclear Transformations and Stability: Involve changes in the nucleus, typically to achieve greater stability. Transformations can include fission, fusion, and radioactive decay such as beta decay.
• Applications: Used in medicine for diagnostic and therapeutic procedures, energy generation in nuclear reactors, and understanding astrophysical processes.

The study of nuclear chemistry encompasses a wide range of scientific pursuits, from everyday applications in nuclear power to advancing our understanding of elemental formation in the universe.