Respuesta :
Answer:
84
Explanation:
From the question given above, it is evident that 222 86Rn is emitting alpha particle since the daughter nuclei produced has a mass number lesser than 4 when compared to parent element.
Therefore, the miss value in the equation is 84.
Please see attachment for further details

Based on the calculations, the missing value that will balance the equation is: A. 84.
What is an alpha decay?
An alpha decay is a type of nuclear reaction in which the atomic nucleus of a radioactive element emits an alpha particle (helium atom), thereby, producing chemical elements with a different atomic nucleus.
In this exercise, we are given the following nuclear equation with an alpha decay:
²²²R₈₆ -----> ²¹⁸Poₓ + ⁴He₂
For the subscript, we have:
86 - 2 = 84.
Read more on alpha decay here: brainly.com/question/23303931
#SPJ2