Final answer:
Barium nitrate dissociates into three ions in solution: one barium ion (Ba2+) and two nitrate ions (NO3-) for a total of three ions per formula unit of the compound.
Step-by-step explanation:
The question pertains to the ionic composition of barium nitrate, which is an ionic compound consisting of barium ions and nitrate ions. When dissociated in water, each formula unit of barium nitrate results in three ions: one barium ion, Ba2+, and two nitrate ions, NO3-. Therefore, the total number of ions in one formula unit of barium nitrate is three.
To further understand this, consider barium nitrate's formula: Ba(NO3)2. Barium (Ba) has a 2+ charge while each nitrate ion (NO3-) has a 1- charge. In order to balance the charges, two nitrate ions are needed for every barium ion. This results in the formula for barium nitrate being Ba(NO3)2, which translates to three total ions when dissociated in solution.