### Naming and Writing Ionic Compounds

```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 Dots
In ionic bonding, electrons are transferred
• Na + Cl
• Cl + Ca
•
•
•
•
•
K+F
Mg + I
Be + S
Na + O
Al + Br
Writing Ionic
Compounds
Guide to Writing Formulas from the Name
Publishing as Benjamin Cummings
5
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
Group 2
2 electrons
Be+2
Br
Group 7
7 electrons
Br-
2. Criss-Cross Charges
• Criss-Cross Charges
• Drop Signs
• Do not write any “1’s”
Be+2 BrBe1Br2
BeBr2
3. Reduce/Simplify
• Reduce any subscripts to the simplest form or
simplest ratio.
• But copper(II) oxide needs to be reduced since
2:2 atoms is the same as 1:1.
+2
Cu
-2
O
 Cu2O2  CuO
Learning Check
Write the formulas of the following ions:
Br−
S2−
N3−
Na+
Al3+
9
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)
+2
Zn (OH)
Zn(OH)2
Learning Check
What is the correct formula for each of the following?
A. Copper(I) nitride
1) CuN
2) CuN3
3) Cu3N
2) PbO
3) Pb2O4
1) PbO2
12
Naming Ionic
Compounds
Naming Ionic Compounds with Two Elements
1. Identify the cation and anion
•Reverse Criss-Cross
Al2S3
+3
Al
-2
S
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
-2
• S = Sulfur  Sulfide
4. Put it together
• Cation name is first
• Anion is second
• Al2S3
+3
-2
• Al S
• Aluminum Sulfide
Learning Check
Write the names of the following compounds.
1) CaO
___________
2) KBr
___________
3) Al2O3
___________
4) MgCl2
___________
19
Solution
Write the names of the following compounds:
1) CaO
calcium oxide
2) KBr
potassium bromide
3) Al2O3
aluminum oxide
4) MgCl2
magnesium chloride
20
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
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
23
Solution
Select the correct name for each.
A. Fe2S3
3) iron (III) sulfide
Fe3+ S2-
B. CuO
3) copper (II) oxide
Cu2+ O2-
24
Learning Check
What is the correct formula for each of the following?
A. Copper(I) nitride
1) CuN
2) CuN3
3) Cu3N
1) PbO2
2) PbO 3) Pb2O4
25
Solution
The correct formula is
A. Copper (I) nitride
3) Cu3N
Need 3Cu+ and N3-