"A nuclear reaction of significant historical note occurred in 1932, when a beryllium target was bombarded with alpha particles. Analysis of the experiment indicated that the following reaction occurred: 4 2He + 9 4Be → 12 6C + ? What is missing in this reaction?"

is missing

Explanation:

In a nuclear reaction, the total mass and total atomic number remains the same.

For the given reaction:

To calculate A:

Total mass on reactant side = total mass on product side

4 + 9 = 12 + A

A = 1

To calculate Z:

Total atomic number on reactant side = total atomic number on product side

2 + 4 = 6 + Z

Z = 0

Hence, missing is .

that's what i got you can count the number of atoms

you didnt put any of the following