What type of reaction is represented by the following equation?$\frac{2}{1}$D$\frac{3}{1}$H → $\frac{4}{4}$He + $\frac{1}{0}$n + energy

Analyzing the question

The equation shows deuterium (²₁H) combining with tritium (³₁H) to give helium and a neutron, with energy released. The notation in the question is garbled (it is written as fractions like 4/4 He instead of ⁴₂He), but the intended reaction is:

²₁H + ³₁H → ⁴₂He + ¹₀n + energy

Concept

• Nuclear fusion: two light nuclei join to form a heavier nucleus, releasing a large amount of energy. This is how the Sun produces energy.
• Nuclear fission: a heavy nucleus (e.g. Uranium-235) is split into smaller nuclei, usually after being hit by a neutron.
• Radioactive (spontaneous) decay: a single unstable nucleus emits particles (α, β, γ) without any other nucleus joining it.

Solution

1. Check the reactants: two small nuclei (deuterium and tritium, both isotopes of hydrogen).
2. Check the product: a heavier nucleus (helium) plus a neutron.
3. Check the balance: • Mass numbers: 2 + 3 = 5, and 4 + 1 = 5 ✓ • Atomic numbers: 1 + 1 = 2, and 2 + 0 = 2 ✓
4. Two light nuclei combine into a heavier one and release energy, so this is nuclear fusion.

(Note: the question's printed notation "4/4 He" appears to be a typo for ⁴₂He.)

Answer: B. Nuclear fusion

Exam tip: Remember "Fusion = Fuse together" (small nuclei join), and "Fission = Fragment" (a big nucleus splits). If you see hydrogen isotopes combining, think fusion.