Question

Give the formulas of compounds in which (a) the cation is \(\mathrm{Ba}^{2+}\), the anion is \(\mathrm{I}^{-}\) or \(\mathrm{N}^{3-}\). (b) the anion is \(\mathrm{O}^{2-}\), the cation is \(\mathrm{Fe}^{2+}\) or \(\mathrm{Fe}^{3+}\).

Short answer

Question: Determine the formulas of the compounds formed from the given cations and anions: a) Cation: \(\mathrm{Ba}^{2+}\), Anions: \(\mathrm{I}^{-}\), \(\mathrm{N}^{3-}\) b) Anion: \(\mathrm{O}^{2-}\), Cations: \(\mathrm{Fe}^{2+}\), \(\mathrm{Fe}^{3+}\) Answer: a) \(\mathrm{BaI_2}\), \(\mathrm{Ba_3N_2}\) b) \(\mathrm{FeO}\), \(\mathrm{Fe_2O_3}\)

Step-by-step solution

Compound with \(\mathrm{Ba}^{2+}\) and \(\mathrm{I}^{-}\) ions

The cation has a +2 charge, and the anion has a -1 charge. To balance the charges, we need to have 2 \(\mathrm{I}^{-}\) ions for every \(\mathrm{Ba}^{2+}\) ion. So the formula for this compound will be \(\mathrm{BaI_2}\).

Compound with \(\mathrm{Ba}^{2+}\) and \(\mathrm{N}^{3-}\) ions

The cation has a +2 charge, and the anion has a -3 charge. To balance the charges, the least common multiple of 2 and 3 is 6, so we need three \(\mathrm{Ba}^{2+}\) ions (+6 charge) and two \(\mathrm{N}^{3-}\) ions (-6 charge). The formula for this compound will be \(\mathrm{Ba_3N_2}\). (b) For this part, we have the anion \(\mathrm{O}^{2-}\) and the cations \(\mathrm{Fe}^{2+}\) and \(\mathrm{Fe}^{3+}\). We need to find the formulas for the compounds formed with these ions.

Compound with \(\mathrm{Fe}^{2+}\) and \(\mathrm{O}^{2-}\) ions

The cation has a +2 charge, and the anion has a -2 charge. To balance the charges, we need one \(\mathrm{Fe}^{2+}\) ion for every \(\mathrm{O}^{2-}\) ion. So the formula for this compound will be \(\mathrm{FeO}\).

Compound with \(\mathrm{Fe}^{3+}\) and \(\mathrm{O}^{2-}\) ions

The cation has a +3 charge, and the anion has a -2 charge. To balance the charges, the least common multiple of 3 and 2 is 6, so we need two \(\mathrm{Fe}^{3+}\) ions (+6 charge) and three \(\mathrm{O}^{2-}\) ions (-6 charge). The formula for this compound will be \(\mathrm{Fe_2O_3}\).