When you place the coefficient 2 in front of tetraiodine nonaoxide (I₄O₉), you effectively double the number of atoms of each element in the formula. Let's break it down:
The formula I₄O₉ indicates there are:
- 4 iodine atoms (I)
- 9 oxygen atoms (O)
When you place the coefficient 2 in front of I₄O₉, the new counts will be:
- Iodine atoms: 2 × 4 = 8
- Oxygen atoms: 2 × 9 = 18
So, the total count after adding the coefficient is:
- 8 iodine atoms and 18 oxygen atoms.
Therefore, the correct answer is: A. 8 iodine atoms and 18 oxygen atoms.