A deuterium nucleus and a tritium nucleus fuse together to produce a helium nucleus and particle X - AQA - A-Level Physics - Question 9 - 2020 - Paper 1

To find the particle X resulting from the fusion of a deuterium nucleus ((^{2}{1}H)) and a tritium nucleus ((^{3}{1}H)), we need to consider the conservation of nucleons and charge.

1. Calculate the total number of nucleons before the reaction:

   • Deuterium has 1 neutron and 1 proton (total 2 nucleons).
   • Tritium has 2 neutrons and 1 proton (total 3 nucleons).
   • Total: 2 + 3 = 5 nucleons.

2. Calculate the total number of nucleons after the reaction:

   • The helium nucleus (^{4}_{2}He) has 2 neutrons and 2 protons (total 4 nucleons).
   • Therefore, particle X must account for the remaining 1 nucleon to maintain balance.

3. Analyze charge conservation:

   • The total charge before the reaction is +2 (1 from deuterium and 1 from tritium).
   • The charge from the helium nucleus is +2, meaning particle X must be neutral in charge to maintain overall charge balance.

Based on this analysis, the only neutral particle that can result from this fusion is a neutron. Therefore, X is a neutron.