Question

Name each of the following compounds, which contain polyatomic ions. a. \(\mathrm{LiH}_{2} \mathrm{PO}_{4}\) b. \(\mathrm{Cu}(\mathrm{CN})_{2}\) c. \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) d. \(\mathrm{Na}_{2} \mathrm{HPO}_{4}\) e. \(\mathrm{NaClO}_{2}\) f. \(\mathrm{Co}_{2}\left(\mathrm{SO}_{4}\right)_{3}\)

Short answer

a. Lithium dihydrogen phosphate b. Copper(II) cyanide c. Lead(II) nitrate d. Sodium hydrogen phosphate e. Sodium chlorite f. Cobalt(III) sulfate

Step-by-step solution

a. Identify ions in LiH2PO4

For LiH2PO4, the ions are Li (Lithium) and H2PO4 (Dihydrogen phosphate).

a. Name LiH2PO4

Since we have a monatomic cation (Li⁺, Lithium) and a polyatomic anion, we name this compound as Lithium dihydrogen phosphate.

b. Identify ions in Cu(CN)2

In Cu(CN)₂, the ions are Cu (Copper) and CN (Cyanide).

b. Name Cu(CN)2

Copper can have different oxidation states. In this case, it has 2 as the subscript in (CN)₂. So the compound is named Copper(II) cyanide.

c. Identify ions in Pb(NO3)2

In Pb(NO₃)₂, the ions are Pb (Lead) and NO3 (Nitrate).

c. Name Pb(NO3)2

Lead also can have different oxidation states; in this case, the total charge of the anions (2 nitrates) is -2, so we know lead has a +2 charge. Thus, we name the compound Lead(II) nitrate.

d. Identify ions in Na2HPO4

In Na₂HPO₄, the ions are Na (Sodium) and HPO4 (Hydrogen phosphate).

d. Name Na2HPO4

The compound consists of monatomic cations (Na⁺) and a polyatomic anion, so it is named Sodium hydrogen phosphate.

e. Identify ions in NaClO2

In NaClO₂, the ions are Na (Sodium) and ClO2 (Chlorite).

e. Name NaClO2

The compound is named Sodium chlorite, as we have a monatomic cation and a polyatomic anion.

f. Identify ions in Co2(SO4)3

In Co₂(SO₄)₃, the ions are Co (Cobalt) and SO4 (Sulfate).

f. Name Co2(SO4)3

Cobalt can also have multiple oxidation states. The charge of the sulfate anions (3 sulfates) is -6; with two cobalt ions, we have a +6 charge. So each cobalt ion has a +3 charge, and we name the compound Cobalt(III) sulfate.