Ionic Compounds usingPolyatomic Ions

Chapter 5

2

What is a Polyatomic Ion?

A cluster of atoms (usually nonmetals) that use molecular bonding within the cluster.

More than one atom covalently bonded (sharing electrons) together carrying a charge (the cluster needs to gain or lose electrons to be satisfied).

3

-ates and -ites

nitriteNO2

-1

sulfiteSO3

-2

phosphitePO3

-3

nitrateNO3

-1

sulfateSO4

-2

phosphate

PO4-3

4

Notable Exceptions

ammonium(a positive polyatomic)

NH4+1

cyanide CN-1

hydroxide OH-1

ferricyanide Fe(CN)6-3

ferrocyanide Fe(CN)6-4

5

What if there’s more than two?

hypochlorite ClO-1

chlorite ClO2-1

chlorate ClO3-1

perchlorate ClO4-1

6

Write the chemical formula for calcium chlorate

• Ca+2 ClO3-1

Ca(ClO3)2

7

Write the chemical formula for aluminum carbonate

• Al+3 CO3-2

Al2(CO3)3

8

Write the chemical formula foriron (III) dichromate

• Fe+3 Cr2O7-2

• note that dichromate does not mean two chromates, it is a particular ion

✓ it got its name for the two chromium’s in the ion, not because there will be two of the polyatomic ions in the compound

Fe2(Cr2O7)3

9

Write the chemical formula for nickel(II) nitrite

• Ni+2 NO2-1

• Note the charge on the nitrite is -1 not 2x-1, the subscript 2 is part of the ion.

Ni(NO2)2

10

Write the chemical formula for gallium cyanide

• not GaCN3

✓ you need 3 cyanides to go with the one gallium

Ga(CN)3

11

Write the name for Mn(SO4)2

Manganese(IV) sulfate

12

Write the name for (NH4)3PO4

Ammonium phosphate• ammonium, NH4

+1 is one of the few positive polyatomic ions

13

Write the name for Ca2Fe(CN)6

• how do you know whether it is ferrocyanide or ferricyanide?

✓ look at the fact that there are 2 Ca+2 ions present

✓ that means that the total cation is +4 and thus the anion must be -4 to match.

calcium ferrocyanide

14

Write the name for AuSCN

gold(I) thiocyanate

15

Write the chemical formula for tin(IV) hydroxide

Sn(OH)4

16

Write the name for CuCO3

copper(II) carbonate

17

Write the chemical formula for copper(I) ferrocyanide

Cu2Fe(CN)6

18

Write the name for CoAs

cobalt(III) arsenide

19

Write the chemical formula for uranium(VI) fluoride

UF6

20

Write the name forcadmium acetate

Cd(C2H3O2)2

21

Write the chemical formula for iron(III) sulfite

Fe2(SO3)3

22

Write the name for Cr(ClO)3

chromium(III) hypochlorite

23

Write the chemical formula for ammonium nitrate

NH4NO3

24

Write the name for Mg(OH)2

magnesium hydroxide

25

Write the chemical formula for K3Fe(CN)6

potassium ferricyanide

26

Write the name for Pb(Cr2O7)2

lead(IV) dichromate

27

It’s all in the name....

28

Which formula contains the most number of “atoms?”

11 atoms 7 atoms

Mn(SO4)2 Cr(ClO)3

29

Which formula contains the greatest number of ions?

3 ions 4 ions

Mn(SO4)2 Cr(ClO)3

30

Which formula has the highest total charge on the anions?

- 4 - 3

Mn(SO4)2 Cr(ClO)3

31

Which formula has the largest molar mass?

55+2(32)+8(16) 52+3(35.5)+3(16)= 247 = 206.5

Mn(SO4)2 Cr(ClO)3