Chapters 4 & 5 – Formation of Compounds

Naming Compounds

And

Writing Formulas

CompoundName of Metal cation(first element)

Name of non metal anion (second element)

Name of compound

Na2O Sodium ion Na1+ Oxide ion O2- Sodium oxide

KF

BaCl2

Al2S3

Ca3N2

LiBr

Ionic Compounds

• Metal bonded to a non-metal (NaCl)– Metals = cations– Non-metals = anions

Naming Ionic Compounds

1. Name the metal first (cation)– The cation name simply is the name of the

element

2. Name the non-metal next (anion)– Anion name is non-metal name with –ide

suffix (oxygen oxide)

KClPotassium chloride

Li2OLithium oxide

NaBrSodium bromide

Writing Ionic Formulas

1. Write the symbol for the metal first with the charge

2. Write the symbol for the nonmetal next with the charge

3. Crisscross the number of the charge

4. All compounds are neutral, so the charges must add to ZERO

EXAMPLES

Aluminum sulfide

Al+3 S-2

Al2S3

Calcium chloride

Ca+2 Cl-1

CaCl2

Magnesium oxide

Mg+2 and O-2

Mg2O2 this can be reduced to

MgO

Naming when the metal forms more than one charge

Look at the Periodic Table – some elements have more than one charge – Transition Metals

Ex: Copper +1 or +2

• Roman Numerals are used to indicate the charge.

Copper (I) or Copper (II)

Cu+1 or Cu+2

Writing

• Copper (II) chloride

CuCl2

Naming

• Determine the charge by working backwards

• Write the charge in roman numerals in the name

CuF2

• Copper is either +1 or +2 charge• In this case it is +2 since there are two Fluorine

atoms for every one copper (F is always -1 charge)• Copper (II) Fluoride

Examples

CrCl3Chromium (III) chloride

EXAMPLES

Fe (III) and CO3

Fe+3 (CO3)-2

Fe2(CO3)3

Metal + Polyatomic

• Polyatomic Ion – Groups of nonmetal atoms bonded together that carry a charge.

• Always include parenthesis around these ions

• End in –ate or –ite– Exceptions – Hydroxide, Cyanide, Ammonium

• Found on the back of your periodic table

Naming

• Metal bonded to a polyatomic ion Al2(SO4)3

– Name the metal– Name the polyatomic ion as it appears on the

back of your periodic table

MgSO4

Magnesium sulfate

CaCO3

Calcium carbonate

Sn(OH)4

Tin (IV) hydroxide

Writing

• Write the symbol for the metal and charge

• Write the polyatomic ion in parenthesis and with charge

• Criss cross the charges

Magnesium hydroxide

Sodium sulfate

Naming Molecular Compounds

• Two non-metals bonded together; shared bond of electronsExample: CO2 = carbon dioxide

• Prefixes are used to express the number of each element

• The second nonmetal ends in –ide

• Never reduce

Prefixes

• (1) mono, (2) di, (3) tri, (4) tetra,

(5) penta, (6) hexa, (7) hepta,

(8) octa, (9) nona, (10) deca

• The prefix mono- is not used with the first named element

Use the back of your periodic table to help you

Name the following:

SO3

Sulfur trioxide

N2O5

dinitrogen pentoxide

C2Br6

dicarbon hexabromide

Write the correct formula:

pentacarbon decahydride

C5H10

tetrasulfur heptoxide

S4O7

carbon monobromide

CBr