Radioactive decay of tritium (hydrogen-3): What is the daughter nuclide produced by its beta decay?

Introduction / Context:
Tritium (symbol T or ³H) is a radioactive isotope of hydrogen with one proton and two neutrons. It undergoes beta minus decay. Understanding its decay product is fundamental in nuclear chemistry, fusion science, environmental tracing, and radiological safety.

Given Data / Assumptions:

• Tritium decays via beta minus (electron) emission.
• Nucleon (mass) number is conserved in beta decay.
• Atomic number increases by one in beta minus decay.

Concept / Approach:
In beta minus decay, a neutron converts to a proton with the emission of an electron and an antineutrino. Therefore, the daughter nucleus has atomic number Z increased by 1, while mass number A remains the same. For tritium (Z = 1, A = 3), the daughter will have Z = 2 and A = 3, which is helium-3 (³He). Options list 'Helium' generally, which correctly captures the element of the daughter nuclide.

Step-by-Step Solution:

Verification / Alternative check:
Published decay schemes universally show ³H → ³He + e⁻ + ν̄ with a half-life of about 12.3 years.

Why Other Options Are Wrong:

• Lithium: Would require Z = 3, not obtained by a single beta minus step from tritium.
• Deuterium: Has A = 2; mass number must remain 3.
• Hydrogen: The product is not another hydrogen isotope because Z increases by 1 in beta minus decay.

Common Pitfalls:
Confusing beta minus with beta plus or forgetting that A stays constant while Z changes by ±1 depending on decay type.

Final Answer:
Helium