Naming Compounds

Unit D.5

IONIC COMPOUNDSPart 1:

Ionic Formulas

• An ionic compound formula is a ratio of the number of cations to anions

• E.g.: CaCl2 will have 1 Calcium atom per 2 chlorine atoms

• The ratios are determined by the charge of each atom

• Calcium has a +2 charge, so there needs to be two chlorine atoms per atom of calcium

+2 -1

For the visual learners out there…

Here’s Calcium Chloride

Balancing Ionic Formulas: Crisscross Method

Ca + Cl

1. Write the charges of each atom based upon its location in the periodic table

2+ -1

2. Bring the numbers down diagonally, ignoring the sign3. Reduce to smallest possible ratio, if necessary. Remove redundant numbers.

21

= CaCl2

Practice

1. Mg + O .

2. Na + S______________ .

3. Sr + Cl .

4. Be + O_______________

5. Li + F .

MgONa2S

SrCl2

BeOLiF

Naming Ionic Compounds

• Number of atoms does not affect naming• The regular name of the metal cation always

comes first• The suffix of the anion changes to –ide• NaCl = Sodium Chloride• NaF = Sodium Fluoride• CaBr2 = Calcium Bromide

Common AnionsElement Name as Anion Example

Sulfur Sulfide Sodium SulfideFluorine Fluoride Calcium FluorideIodine Iodide Potassium Iodide

Bromine Bromide Strontium BromideChlorine Chloride Sodium ChlorideOxygen Oxide Iron Oxide

Nitrogen Nitride Barium NitrideCarbon Carbide Tungsten Carbide

Phosphorous Phosphide Nickel Phosphide

Try these.

1. Na2S2. Li3N3. Ag2O4. CaBr2

5. K2O6. SrCl2

________________

________________

________________

________________

________________

________________

Sodium SulfideLithium Nitride

Silver Oxide

Calcium BromidePotassium Oxide

Strontium Chloride

Ions with multiple charges

• Transition metals can have different ionic states

• Iron, for example, can sometimes have a +2 charge, while other times it will have a +3

• To avoid confusion, we notate Iron with a +2 charge as Iron(II), while Iron with a +3 charge would be Iron(III)

Demo

• Iron(III) Oxide = Fe3+ + O2- = Fe2O3

Iron(II) Oxide = Fe2+ + O2- = FeO

Now try these

1. FeO______________

2. Fe2O3

_____________________

3. NiBr3

_____________________

4. CrO______________

5. Cr2O3

_____________________

Iron(II) Oxide

Iron(III) Oxide

Nickel(III) Bromide

Chromium(II) Oxide

Chromium(III) Oxide

Writing Formulas from Names

• Use periodic trends to predict ionic charges of atoms (Group I = +1, Group II = +2, etc)

• Overall charge of compound should equal 0• Use the “crisscross method” to assign number

of atoms & reduce to lowest # ratio• “Sodium Fluoride” = Na+ + F- =• “Calcium Chloride” = Ca2+ + Cl- = CaCl2

NaF

Practice

1. Calcium Bromide2. Potassium Sulfide3. Nickel(II) Iodide4. Copper(II) Oxide5. Strontium Fluoride

Polyatomic ions

• Some molecules have an overall charge, like ions

• These are called polyatomic ions

• They are treated as a single unit and can NOT be separated!

• Naming system is otherwise the same

Barium Sulfate

Balancing polyatomic ions

Al+3 + SO42-

Al2(SO4)3

Treat the entire polyatomic ion as 1 unit

For balancing, place the polyatomic anion in parenthesis

( )32

Naming Conventions are the same as regular ions

Aluminum Sulfate

Balance and name the following using

1. Na + SO42-

_______________________2. Ca + OH-

_______________________3. Mg + NO3

-

_______________________4. Sr + CO3

2-

______________________5. NH4

+ + NO3-______________________

Na2SO4 Sodium SulfateCa(OH)2 Calcium Hydroxide

Mg(NO3)2 Magnesium Nitrate

SrCO3 Strontium CarbonateNH4NO3 Ammonium Nitrate

Naming Covalent Compounds

• Number of atoms is represented by prefix• All atoms in a molecule have their own

separate prefixes and are listed in order of appearance

• First element only has a prefix if it is greater than 1

• Last element ends in -ide

Prefix # of atoms Example Formula

mon 1 Carbon Monoxide CO

di 2 Carbon Dioxide CO2

tri 3 Sulfur Trioxide SO3

tetra 4 Carbon tetrachloride CCl4

penta 5 dinitrogen pentoxide N2O5

hexa 6 Sulfur hexafluoride SF6

hepta 7 Iodine heptafluoride IF7

octa 8 heptaphosphorous Oxtafluoride P7F8

nona 9 tetraiodine nonafluoride I4F9

deca 10 Disulfur decafluoride S2F10

Practice

1. CO____________

2. NO2

__________________

3. SF2

__________________

4. CCl4

__________________

5. NI3

__________________

Carbon Monoxide

Nitrogen dioxide

Sulfur difluoride

Carbon tetrachloride

Nitrogen triiodide

Naming Acids

• All* Acids begin with Hydrogen

• HCl, H2SO4, HNO3, etc• Although there is a

naming system, most scientists just memorize them