A deuterium nucleus and a tritium nucleus fuse together to form a helium nucleus and a particle X - AQA - A-Level Physics - Question 30 - 2019 - Paper 2

To identify particle X in the fusion process of a deuterium nucleus and a tritium nucleus, we first analyze the nuclear reaction. The given equation represents the fusion of a deuterium ( $_{1}^{2}H$) and a tritium nucleus ( $_{1}^{3}H$) to produce a helium nucleus ( $_{2}^{4}He$) and a particle X.

1. Conservation of Nucleons: In nuclear reactions, the total number of nucleons (protons + neutrons) must be conserved. The deuterium nucleus has 2 nucleons and the tritium nucleus has 3 nucleons, giving a total of 5 nucleons on the left side. The helium nucleus has 4 nucleons, therefore:

   $ext{Nucleons from X} = 5 - 4 = 1$

2. Identifying X: Since X represents a single nucleon, it can either be a proton or a neutron. Looking at the options:

   • A. electron (not a nucleon)
   • B. neutron (can be a valid option)
   • C. positron (not a nucleon)
   • D. proton (another valid option)

3. Conclusion: Given that the reaction usually indicates the release of a proton in fusion reactions involving light nuclei, the most appropriate choice is D. proton. Therefore, X is identified as a proton.