1. Naming Compounds and Molecules

2. The FIRST thing you must do is decide if the compound is IONIC or COVALENT.
Why? Each type of compound is named differently!

3. If it is Covalent… Follow the prefix method
One Mono-
Two Di-
Three Tri-
Four Tetra-
Five Penta-
Six Hexa-
Seven Hepta-
Eight Octa-
Nine Nona-
Ten Deca-
Follow the prefix method
Affix the following prefixes to each element indicating how many there are.

4. Other Covalent Rules
Name the element farther left on the periodic table first.
If the first element only has one atom, the “mono-” is dropped.
On the last word, the suffix is dropped and the ending –ide is added.

5. Covalent Examples
CO2
There is only one carbon, so the “mono-” is dropped.
There are two oxygen atoms = Di
Carbon Dioxide CO
There is one oxygen atom = mono
Carbon Monoxide

6. A few more Covalent Examples
Tetracarbon Difluoride
There are four carbon atoms
There are two fluorine atoms
C4F2
Dihydrogen Monoxide
There are two hydrogens
There is one oxygen
H2O

7. Let’s try ionic compounds…
That was easy, Right?
Let’s try ionic compounds…

8. If it is Ionic… Ionic compounds DO NOT have prefixes.
Example: Write the formula for Aluminum Fluoride
How do you do it???
Let’s think about it practically, first.
How? Draw the Bohr model for each and figure out how many of each atom are needed.

9. Another Way to Think about It…
Aluminum needs to give 3 electrons away.
Fluorine only needs one electron
You need 3 fluorines to take all of aluminum’s electrons
AlF3

10. That Seems Like A lot of work. Is There Another Way to Think About It???
YES!!!
Step 1: Determine the Charge of the ion.
How? What would its charge be if its outer energy level were full?
First, write the element’s symbol and then its charge as a superscript
Example: Aluminum Fluoride

11. Aluminum How many valence electrons does Aluminum have? 3
What will Aluminum do with these?
Give them away.
13+ (protons)
10- (electrons)
3+ (total charge)
Al+3

12. What about Fluorine? How many valence electrons does fluorine have? 7
What does fluorine need to be like a noble gas?
One more electron
9+ (protons)
10- (electrons)
-1 (total charge)
F-1

13. A positive ion is called a CATION.
A negative ion is called an ANION.
The metal is always listed first, the nonmetal second.
The ending of the nonmetal is dropped and the ending –ide is added.

14. Now What?
Step 2: Write each symbol and charge– write the metal first, the nonmetal second
Al F
Step 3: Follow the Criss-Cross Rule
Aluminum’s charge becomes fluorine's subscript and vice versa
The charge symbols are dropped (the + or -) +3 -1

15. Final Formula
AlF3

16. Another Example: Sodium Oxide
Step 1: Find the charges of the ions
Sodium has 1 valence electron
It gives the electron away
Charge is +1
Oxygen has 6 valence electrons
It needs two more electrons
Charge is –2
Na+1 O-2

17. Step 2: Write each symbol and charge
Na O
Step 3: Follow the Criss-Cross Rule -2 +1

18. Final Formula for Sodium Oxide
Na2O

19. Another Way to Think About It: Using Lewis Dot Structures
Draw the Lewis Dot for each element
Sodium only has one electron to give.
In order for oxygen to be like a noble gas, there must be two sodiums.
Na2O Na O Na

20. Name the Following Ionic Compounds
BaBr
Remember, NO PREFIXES NEEDED!!
Barium Bromide
K3P
Potassium Phosphide
Rb2S
Rubidium Sulfide

21. Transition Metals Transition metals can often make more than one ion.
The ion charge is written as a ROMAN NUMERAL after the metal
The charges of metals are ALWAYS positive.
Examples:
Iron (III) Fe+3
Copper (II) Cu+2
Remember, when naming ionic compounds, if it is a transition metal, to include the roman numeral!

22. Example with a Transition Metal
Copper (II) Chloride
Step 1: Find the charges of the ions
We already know copper’s charge from the roman numeral (remember, metals always have a POSITIVE charge)
Cu+2
Chlorine has 7 valence electrons
Chlorine needs 1 electron
Charge is –1
Cl-1

23. Step 2: Write the Symbols & Charges
Cu Cl
Step 3: Follow the Criss-Cross Rule -1 +2

24. Final Formula for Copper (II) Chloride:
CuCl2

25. Another way to Think About it Using Lewis Dot Structures
First, draw the Lewis Dot for each element.
Copper gives away two electrons
Chlorine needs one electron
It takes 2 chlorines to take all of copper’s electrons.
Final Answer: CuCl2 Cl Cu Cl

26. If it is Polyatomic…
You will recognize a polyatomic (in most cases) by the ending of the last word in the name.
Many polyatomics DO NOT end in –ide
Examples: Sulfate, Nitrite, Carbonate
Examples that end in –ide: Hydroxide, Cyanide
Polyatomics already give you the charge of the ion (just look it up on a chart)
Write the metal first, the polyatomic second, then follow the rules of ionic bonding.
If more than one polyatomic is needed, put the entire polyatomic in parentheses and put the subscript outside the parentheses.

27. Polyatomic Example Lithium Sulfate
Step 1: Find the charges of the ions
Lithium has 1 valence electron.
Lithium gives the electron away = +1 charge
Li+1
Sulfate…look it up on a chart
SO4-2

28. Step 2: Write the Symbols & Charges
Li SO4
Step 3: Follow the Criss-Cross Rule -2 +1

29. Final Formula for Lithium Sulfate
Li2(SO4)1

30. OK, time for more practice. See the practice sheet…. 