Ionic Compounds With Poly-atomic Ions (no Transition Metals)

Mg2+ ion will form a compound with one cation and two nitrate ions. Mg2+ will form the compound Mg(NO3)2 because nitrate has the formula NO3—. If a compound has two anions each with a 1- charge, then a cation with a 2+ charge is needed to form the compound.

The formula for the compound would be Mg3(PO3)2 having x = 3 and y = 2 because magnesium forms an ion with a 2+ charge and phosphite has a 3- charge. To balance the charges between the ions, the compound has three magnesium ions for a total of 6+ and two phosphite ions for a total of 6-.

(NH4)3PO4 is the formula for the compound formed from the ammonium (NH4?) and phosphate (PO43-) ions. Since ammonium has a 1+ charge, three are needed to balance the 3- charge of the phosphate ions.

The correct name for Mg(HSO4)2 is magnesium hydrogen sulfate or magnesium bisulfate. Magnesium sulfate would have the formula MgSO4, and a Roman numeral is not needed since magnesium is an alkaline earth metal and has only one possible charge.

The formula for aluminum hydroxide is Al(OH)3. Aluminum has a 3+ charge and hydroxide has the formula OH—. Therefore, three hydroxide ions, each with a 1- charge, are needed to balance the 3+ charge for the aluminum.

Permanganate has the formula MnO4—.

K+ can correctly complete the formula, which results in K2HPO4. Because two cations are needed to balance the charge on hydrogen phosphate (HPO42-), the cation must have a 1+ charge.

Na+ will form a compound with bicarbonate with a 1:1 cation to anion ratio. Bicarbonate, an anion also known as hydrogen carbonate, has the formula HCO3—. Since bicarbonate is an anion with a 1- charge, it will form a 1:1 ratio with a cation with a 1+ charge.

The bisulfite, also known as hydrogen sulfite, has the formula HSO3

Sulfite

For the compound Nax(CrO4)y, x = 2 and y = 1 giving the formula Na2CrO4 which is named sodium chromate. Two sodium ions (each with a 1+ charge) are needed to balance the 2- charge for the chromate ion.

Ca(H2PO4)2 is the correct formula for dihydrogen phosphate. Dihydrogen phosphate has the formula H2PO4—, so two ions are needed to balance the 2+ charge of the calcium ion.

The formula for carbonate ion is CO32-.

Dichromate, Cr2O72-, will complete the formula and form Al2(Cr2O7)3. Aluminum has a 3+ charge and the anion needs a 2- charge to balance the charges in the compound. Two aluminum ions (2 × 3+) have a total charge of 6+ to balance with the 6- charge of the three dichromate ions (3 × 2-).

Li+ will form a compound with chlorate with a 1:1 ratio to form the compound LiClO3. Chlorate has the formula ClO3—. To have a compound with a 1:1 ratio with chlorate, you need a cation with a 1+ charge.

The formula for the peroxide ion is O22-. Hydrogen peroxide, commonly found in medicine cabinets and referred to as "peroxide", has the formula H2O2.

The formula for aluminum hydroxide is Al(OH)3. Aluminum has a 3+ charge and hydroxide has the formula OH—. Therefore, three hydroxide ions, each with a 1- charge, are needed to balance the 3+ charge for the aluminum.

Hydrogen carbonate, also known as bicarbonate, has the formula HCO3—.

BaSO4 has the name barium sulfate. A Roman numeral is not needed because barium is an alkaline earth metal and only has one possible charge.

The formula for potassium iodate is KIO3. The iodate ion, IO3¯, has a 1- charge, so it will form a compound with a 1:1 ratio with the potassium ion, which has a 1+ charge.