The nuclear equation is incomplete. 1 to the 1th power cap h plus 7 to the 15th power cap n rightarrow ? plus 2 to the 4th power He What particle completes the equation?

Conserve mass number and atomic number in the equation. The reactants have a total mass number of 1 + 15 = 16 and atomic number of 1 + 7 = 8. After accounting for helium-4, the missing particle must have mass number 16 − 4 = 12 and atomic number 8 − 2 = 6. That particle is carbon-12, choice D.

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