Two protons and two neutrons are released as a result of this reaction. 86 to the 222th power Rn rightarrow 84 to the 218th power Po plus ? Which particle is released?

An alpha particle contains two protons and two neutrons, exactly the particles released. The nucleus changes from radon-222 to polonium-218, losing 4 from its mass number and 2 from its atomic number, which matches one alpha particle.

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