Answer:
1 x 10^13 stadiums will be needed in this scenario 
Step-by-step explanation:
We are told that 
1 stadium holds = 1 × 10^5 people and 
Number of iron atoms = 1 × 10^18 atoms
If the stadium carries an equivalent number of atoms as that of people.
We can infer that 1 stadium will carry 1 × 10^5 atoms.
The calculation to determine the number of stadiums would then be 1 × 10^18 divided by 10^5 atoms/stadium which was gotten by dividing the total number of atoms by the number of atoms per stadium.
Number of stadiums = Total number of atoms ÷ Number of atoms per stadium
 = 1 × 10^18 atoms ÷ 1 × 10^5 atoms/stadium
 = 1 × 10^13 Stadiums
This means that 1 × 10^18 atoms would occupy 1 × 10^13 stadiums