Question

case 3. ionic compounds with polyatomic ions. cases 1 and 2 above involve ionic compounds that consist of a metal cation and a non - metal anion - two types of elements only. these are called binary compounds. now let us turn to ionic compounds that are formed from polyatomic ions: (mostly ternary compounds) you must learn the names and formulas for all the polyatomic ions assigned in lecture. note c₂o₄²⁻ (oxalate) is another common ion but you do not need to memorize it. as with all ionic compounds, the cation is named first, then the anion: examples: (nh₄)₂s ammonium sulfide k₃po₄ potassium phosphate zn(no₃)₂ zinc nitrate fe₂(so₄)₃ iron (iii) sulfate (or ferric sulfate) cuco₃ copper (ii) carbonate (or cupric carbonate) note: parentheses ( ) are used only when there are 2 or more polyatomic ions. exercise: name the following: (nh₄)₂o ____________ na₂so₃ __________ fec₂o₄ __________ or __________ cuno₂ __________ or __________ zn₃(po₄)₂ __________ ca(hso₄)₂ __________ sn(no₂)₂ __________ or __________ exercise: give formulas for the following: copper (ii) nitrate __________ lithium phosphate __________ silver carbonate __________ chromium (ii) hydroxide __________ barium permanganate __________ lead (ii) cyanide __________ nickel hydroxide __________ magnesium bicarbonate __________ potassium dichromate __________ aluminum hydrogen sulfate ____________

Explanation:

Step1: Recall naming rules

For ionic compounds with poly - atomic ions, name the cation first then the anion.

Step2: Name $(NH_4)_2O$

The cation is ammonium ($NH_4^+$) and the anion is oxide ($O^{2 -}$), so it is ammonium oxide.

Step3: Name $FeC_2O_4$

The cation is iron(II) (since $C_2O_4^{2 -}$ has a - 2 charge and compound is neutral) and the anion is oxalate, so it is iron(II) oxalate.

Step4: Name $CuNO_2$

The cation is copper(I) (since $NO_2^-$ has a - 1 charge and compound is neutral) and the anion is nitrite, so it is copper(I) nitrite.

Step5: Name $Zn_3(PO_4)_2$

The cation is zinc and the anion is phosphate, so it is zinc phosphate.

Step6: Name $Sn(NO_2)_2$

The cation is tin(II) (since $NO_2^-$ has a - 1 charge) and the anion is nitrite, so it is tin(II) nitrite.

Step7: Name $Na_2SO_3$

The cation is sodium and the anion is sulfite, so it is sodium sulfite.

Step8: Name $Ca(HSO_4)_2$

The cation is calcium and the anion is hydrogen sulfate, so it is calcium hydrogen sulfate.

Step9: Find formula for copper(II) nitrate

Copper(II) is $Cu^{2+}$ and nitrate is $NO_3^-$, so the formula is $Cu(NO_3)_2$.

Step10: Find formula for silver carbonate

Silver is $Ag^+$ and carbonate is $CO_3^{2 -}$, so the formula is $Ag_2CO_3$.

Step11: Find formula for barium permanganate

Barium is $Ba^{2+}$ and permanganate is $MnO_4^-$, so the formula is $Ba(MnO_4)_2$.

Step12: Find formula for nickel hydroxide

Nickel(II) (assuming common oxidation state) is $Ni^{2+}$ and hydroxide is $OH^-$, so the formula is $Ni(OH)_2$.

Step13: Find formula for potassium dichromate

Potassium is $K^+$ and dichromate is $Cr_2O_7^{2 -}$, so the formula is $K_2Cr_2O_7$.

Step14: Find formula for lithium phosphate

Lithium is $Li^+$ and phosphate is $PO_4^{3 -}$, so the formula is $Li_3PO_4$.

Step15: Find formula for chromium(II) hydroxide

Chromium(II) is $Cr^{2+}$ and hydroxide is $OH^-$, so the formula is $Cr(OH)_2$.

Step16: Find formula for lead(II) cyanide

Lead(II) is $Pb^{2+}$ and cyanide is $CN^-$, so the formula is $Pb(CN)_2$.

Step17: Find formula for magnesium bicarbonate

Magnesium is $Mg^{2+}$ and bicarbonate is $HCO_3^-$, so the formula is $Mg(HCO_3)_2$.

Step18: Find formula for aluminum hydrogen sulfate

Aluminum is $Al^{3+}$ and hydrogen sulfate is $HSO_4^-$, so the formula is $Al(HSO_4)_3$.

Answer:

$(NH_4)_2O$: ammonium oxide
$FeC_2O_4$: iron(II) oxalate
$CuNO_2$: copper(I) nitrite
$Zn_3(PO_4)_2$: zinc phosphate
$Sn(NO_2)_2$: tin(II) nitrite
$Na_2SO_3$: sodium sulfite
$Ca(HSO_4)_2$: calcium hydrogen sulfate
copper(II) nitrate: $Cu(NO_3)_2$
silver carbonate: $Ag_2CO_3$
barium permanganate: $Ba(MnO_4)_2$
nickel hydroxide: $Ni(OH)_2$
potassium dichromate: $K_2Cr_2O_7$
lithium phosphate: $Li_3PO_4$
chromium(II) hydroxide: $Cr(OH)_2$
lead(II) cyanide: $Pb(CN)_2$
magnesium bicarbonate: $Mg(HCO_3)_2$
aluminum hydrogen sulfate: $Al(HSO_4)_3$