What balanced equation represents nuclear fusion?
Nuclear fusion is a process in which two or more atomic nuclei collide at a very high speed and join to form a new type of atomic nucleus that has more mass than any of the starting nuclei.
In order to write an equation for such a reaction, we must first establish some basic rules. Each of the elements involved in the reaction is identified by the chemical symbol. Two numbers are attached to the symbol. The number at the upper left is the mass number, also known ‘A’. The A identifies the number of protons and neutrons in the nucleus. The number at the lower left is the atomic number or Z. The Z describes the number of protons in the nucleus and determines the type of atom. Thus, the symbol for uranium-238 is ₉₂²³⁸ U (Sorry, the 92 should be directly under the 238, but I can’t do that in this editor).
We also use symbols for α and β particles and for protons and neutrons:
α = ₂⁴He; β = ₋₁⁰e; proton = ₁¹H; neutron = ₀¹n
Just as in a balanced chemical equation, in a balanced nuclear equation, the sums of the superscripts and the sums of the subscripts must be equal on each side of the equation.
Now that we know what these symbols represent, let's see how they can be applied to a nuclear fusion. A typical example is the fusion of two deuterium nuclei to form a tritium nucleus and a proton:
₁²H + ₁²H → ₁³H + ₁¹H
Notice how, on each side of the equation, the superscripts add up to 4 and the subscripts add up to 2.
Here are some other examples:
₁²H + ₁³H → ₂⁴He + ₀¹n
₁²H + ₂³He → ₂⁴He + ₁¹H
₁³H + ₁³H → ₂⁴He + 2₀¹n
₂³He + ₂³He → ₂⁴He + 2₁¹H
In each case, the two reactant nuclei give a product that has more mass than either of them. These are examples of nuclear fusion.