Ionic Compounds

This is Important!

• On the Periodic Table… remember where to:

and the nonmetals find the metals

If You Don’t Remember How to Tell Metals From

Nonmetals, Nothing in This Chapter Will Make Sense!

Ionic Compounds

There are two types of

ionic compounds…

1. Binary ionic compounds and…

2. Ionic compounds that contain

“polyatomic ions”.

Binary Ionic Compounds

Type 1: Binary Ionic Compounds

1. “Binary” means 2…

(as in “bicycle”… “2 wheels”)

A binary ionic compound has only…

…2 elements:

(example: BaCl2)

1.The first element is always a metal!

2.The second element is always a nonmetal!

Type 1: Binary Ionic Compounds

• “2 elements” means just that… “2 elements”!

There can be more than one ion of an element!

• Example: AlF3

AlF3 contains only 2 elements: Al & F.

AlF3 has 1 Al+3 ion, and 3 F-1 ions.

{metal (+) & nonmetal (-)}

The subscript tells you how many ions are in

the compound… (a “1” is understood and not written)

Naming Binary Ionic Compounds

Naming Binary Ionic Compounds

• To name a binary ionic compound…

1. Write the name of the metal ion (+)…

(this is just the name of the metal)

2. Write the name of the nonmetal ion (-)…

(the nonmetal ion has the same “root” as

the nonmetal, but with an “-ide” suffix).

Examples: “chlorine” becomes “chloride”

“oxygen” becomes “oxide”

“nitrogen” becomes… “nitride”

That’s It!!

Naming Binary Ionic Compounds

Just write the metal ion name first, then the

nonmetal ion name second!

(remember the “ide” nonmetal ending)

Practice: (name these)…

K2S

MgO

Sr3As2

potassium sulfide

magnesium oxide

strontium arsenide

Writing the Formula of a Binary Ionic Compound

• Remember, metals are always (+) because

they lose electrons, and

• Nonmetals are always (-) because

they gain electrons!!

• In any ionic compound,

the total (+) must EQUAL the total (-)!!

Writing Binary Ionic Compounds

• To write a binary ionic compound formula…

• …you must know the charge …

• …of the metal ion and the nonmetal ion!

• There are two ways to know these…

…Memorize them, or

…Look at the periodic table!

Guess which is easier?!

Writing Binary Ionic Compounds

You Guessed it!

The “representative” elements are easy! +1

+2

+3

Each family has

its own charge! -3 -2 -1

0

Noble gas

“wannabe’s”,

remember?

In Family IVA (14), only Sn and Pb form ions

Writing Binary Ionic Compounds

IVA

• The transition metals do not follow any simple

rules. (Many can even have two possible

charges!)

• Some must be memorized, but, there IS an

easy system for the others…

• The Roman Numeral after the name gives you

the (+) charge!

• Examples: “copper(I)” = Cu+1

“iron(III)” = Fe+3

“lead(IV)” =

Writing Binary Ionic Compounds

Pb+4

• IONIC COMPOUNDS ARE NEUTRAL!!

• Be sure the (+) charges = the (-) charges!

• Example: “aluminum fluoride”

Writing Binary Ionic Compounds

aluminum ions are Al+3 fluoride ions are F-1

Al+3 F-1 AlF3 (Al+3 + F-1 + F-1 + F-1)

Adds up to zero! The compound has

NO charge!

Practice: write the formula for:

Writing Binary Ionic Compounds

calcium fluoride

lithium phosphide

aluminum oxide

+2

-1 CaF2 +3

Al2O3

+1

-3

Li3P

-2

copper(II) chloride CuCl2 Cu+2 and Cl-1

Writing Binary Ionic Compounds

Ionic formulas are “formula units” of ionic

compounds…

…ionic compounds can’t form molecules!

Remember to reduce any ionic formula to a

lowest ratio… Example: barium oxide

Ba+2 O-2 Ba2O2? Reduce to “BaO”

Special Note: be SURE to write element symbols

clearly! Lower and upper case letters must be obvious!

Compounds Containing Polyatomic Ions

Type 2: Ionic Compounds

Containing “Polyatomic Ions”

•Polyatomic ions are GROUPS of atoms

with a charge!

(most will have a negative (-) charge, just

like a non-metal ion)

You will be given a list of these to use…

O

• “poly” means “many”, so…

• “polyatomic” means “many atoms”!

• (These are ions made of groups of atoms)!

Polyatomic Ions

An example: the

polyatomic ion,

“nitrate”… N

O O

-1

This group of atoms carries a charge of (-1).

Nitrate’s

formula is:

NO3-1

…contains 1 nitrogen and 3 oxygen atoms!

Naming Compounds with Polyatomic ions

Naming Ionic Compounds With

Polyatomic Ions

• To name an ionic compound with polyatomic

ions is really EASY…

1.Write the name of the positive ion (+)…

(usually the name of the metal)

2.Write the name of the negative ion (-)…

(usually the polyatomic ion)

That’s IT!!

• Example: Mg(NO3)2 “magnesium nitrate”

Writing the Formula of a Compound That Contains

Polyatomic Ions

• To write a formula using polyatomic ions,

…you must know the formula and charge …

…of the metal ion and the polyatomic ion.

• The metal ions you know (periodic table)…

…you will have a list of polyatomic ions

with their formulas and charges.

Formulae with Polyatomic ions

• In ALL ionic compounds, the total (+) must be

equal to the total (-)!!

• Just look at the charges, and make sure they

add up to zero.

Formulae with Polyatomic ions

“sodium” = Na+1 “carbonate” = CO3-2

Na+1 CO3-2

“Na2CO3”

+ Na+1 Na+1 + CO3-2

Adds up to zero!

Example: “sodium carbonate”

• What if more than one polyatomic ion is needed?

• Wrap the polyatomic ion in parenthesis!

• Example: “aluminum sulfate”

aluminum ions are Al+3 sulfate ions are SO4-2

Al+3 SO4-2

(Al+3 + Al+3 +

Adds up to zero!

Formulae with Polyatomic ions

SO4-2 + SO4

-2 + SO4-2)

2 Al+3 3 SO4-2

Al2(SO4)3

A Final Note

•Some ionic compounds “collect” water from

the moisture in the air.

•They trap this “collected water” in their

crystals.

•When they have trapped this water, they are

called “hydrates”.

•Their formula includes water, written after a

raised dot: MgSO4 · 5H20

(magnesium sulfate pentahydrate)

*(Prefixes

in your

notes) *