Naming and Writing Ionic Compounds

Ionic Compounds

• Occur between a metal and non-metal• Occur when electrons are transferred

between atoms forming ions• Metals make cations = positive ions• Nonmetals make anions = negative ions• Also use these rules when a polyatomic ion is

present

Ionic Bonding Using Lewis DotsIn ionic bonding, electrons are transferred

• Na + Cl• Cl + Ca

• K + F• Mg + I• Be + S• Na + O• Al + Br

Writing Ionic Compounds

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Guide to Writing Formulas from the NameCopyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

1. Identify the Ions• Look at the group they are in on the periodic table• Determine the type of ion created and assign an

oxidation number (charge)

Be Br Group 2 Group 7 2 electrons 7 electrons Be+2 Br-

2. Criss-Cross Charges• Criss-Cross Charges• Drop Signs• Do not write any “1’s”

Be+2 Br-

Be1Br2

BeBr2

3. Reduce/Simplify

• Reduce any subscripts to the simplest form or simplest ratio.

• LiBr2 is already simplified• But copper(II) oxide needs to be reduced since

2:2 atoms is the same as 1:1.

Cu+2 O-2 Cu2O2 CuO

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Learning CheckWrite the formulas of the following ions:

Br− S2− N3−

Na+

Al3+

Other Things to Watch for…

• Roman Numerals– The numeral in the parenthesis is the charge– Only occur with Transition Metals– copper(II) oxide = Cu+2 O-2

• Polyatomic Ions– Use the same rules– Place entire polyatomic ion in parenthesis when

criss-crossing

Example

• Zinc(II) Hydroxide –Zn = Transition Metal = Zn+2

–OH = Polyatomic ion = (OH)-

Zn+2 (OH)-

Zn(OH)2

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Learning CheckWhat is the correct formula for each of the following?A. Copper(I) nitride

1) CuN 2) CuN3 3) Cu3N

B. Lead(IV) oxide 1) PbO2 2) PbO 3) Pb2O4

Naming Ionic Compounds

Naming Ionic Compounds with Two Elements

1. Identify the cation and anion

•Reverse Criss-CrossAl2S3

Al+3 S-2

2. Name the Cation

Al+3 S-2

• The cation is the positive ion• Use its element name • Al+3 = Aluminum

3. Name the Anion

Al+3 S-2

• The anion is the negative ion• Use the element name, but

change the last part to -ide• S-2 = Sulfur Sulfide

4. Put it together

• Cation name is first• Anion is second• Al2S3

• Al+3 S-2

• Aluminum Sulfide

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Write the names of the following compounds.

1) CaO ___________

2) KBr ___________

3) Al2O3 ___________

4) MgCl2 ___________

Learning Check

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Write the names of the following compounds:

1) CaO calcium oxide

2) KBr potassium bromide

3) Al2O3 aluminum oxide

4) MgCl2 magnesium chloride

Solution

Other Things to Watch for…

• Roman Numerals– Needed if contains a transtition metal – Write in parenthesis after element name– Cu+2 O-2 = copper(II) oxide

• Polyatomic Ions– Use the same rules– Name polyatomic by its name

Example:• Pb = Lead (a transition metal)• NO3 is a polyatomic ion

• Pb(NO3)2

• Pb+2 NO3-1

• Lead (II) Nitrate

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Learning Check

Select the correct name for each.A. Fe2S3

1) iron sulfide 2) iron(II) sulfide 3) iron(III) sulfide

B. CuO 1) copper oxide 2) copper(I) oxide 3) copper(II) oxide

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Solution

Select the correct name for each.A. Fe2S3

3) iron (III) sulfide Fe3+ S2-

B. CuO 3) copper (II) oxide Cu2+ O2-

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Learning Check

What is the correct formula for each of the following?A. Copper(I) nitride

1) CuN 2) CuN3 3) Cu3N

B. Lead(IV) oxide 1) PbO2 2) PbO 3) Pb2O4

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Solution

The correct formula isA. Copper (I) nitride

3) Cu3N Need 3Cu+ and N3-

B. Lead (IV) oxide 1) PbO2 Need Pb4+ and 2O2-