Complete the nuclear equation
218/84po −→ 4/2he +? .
1. ? = 222/86rn
2. ? = 222/86pb
3. none of these
4. ? = 214/82rn
5. ? = 214/82pb
6. ? = 222/86po
7. ? = 214/82po

In order to solve this question, we must apply the conservation of mass. The total number of nucleons (upper number) and protons (lower number) must be equal before and after the decay. The new nucleon number is
218 - 4
= 214
And new proton number is
84 - 2
= 82
Next, we must identify which element has the proton number 82. That would be lead, Pb.
Therefore, the answer is 
5. ²¹⁴Pb₈₂

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