1. Chapter 7 Notes Chemical Formulas West Valley High School
&
Chemical Compounds
West Valley High School
General Chemistry
Mr. Mata

2. Standard 3d
Determine the molar mass of a molecule from its chemical formula and atomic masses.

3. Essential Question
How do you write chemical formulas for chemical compounds using a set of standard rules?

4. Ions
Ions: atom (groups of atoms = polyatomic ions) that have a charge.
Number of protons (p+) is not equal to the number of electrons (e-).
p+≠ e-
Cation: A positive ion
Mg2+, NH41+
Anion: A negative ion
Cl 1 -, SO42 -
Ionic Bonding: Force of attraction between oppositely charged ions.

5. Predicting Ionic Charges
Group 1:
Lose 1 e- to form +1 ions
H+1
Li+1
Na+1
K+1

6. Predicting Ionic Charges
Group 2:
Loses 2 e-’s to form +2 ions
Be+2
Mg+2
Ca+2
Sr+2
Ba+2

7. Predicting Ionic Charges
Loses 3
e-’s to form
+3 ions
Group 13:
B+3
Al+3
Ga+3

8. Predicting Ionic Charges
Lose 4
e-’s or gain
4 e-’s?
Group 14:
Neither! Group 14 elements rarely form ions.

9. Predicting Ionic Charges
Nitride
Gains 3
e-’s to form
-3 ions
Group 15:
P-3
Phosphide
As-3
Arsenide

10. Predicting Ionic Charges
Oxide
Gains 2
e-’s to form
-2 ions
Group 16:
S-2
Sulfide
Se-2
Selenide

11. Predicting Ionic Charges
F-1
Fluoride
Br-1
Bromide
Group 17:
Gains 1
e- to form
-1 ions
Cl-1
Chloride
I-1
Iodide

12. Predicting Ionic Charges
Stable Noble gases do not form ions!
Group 18:

13. Predicting Ionic Charges
Many transition elements
have more than one possible oxidation state.
Groups :
Iron(II) = Fe+2
Iron(III) = Fe+3

14. Predicting Ionic Charges
Some transition elements
have only one possible oxidation state.
Groups :
Zinc (II) = Zn+2
Silver (I) = Ag+1

15. Writing Ionic Compound Formulas
Example: Iron(III) chloride
1. Write the formulas for the cation and anion, including CHARGES!
Fe+3
Cl-1
2. Check to see if charges are balanced. 3
3. Balance charges , if necessary, using subscripts.
Not balanced!
FeCl3

16. Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
Al+3
S-2 2 3
3. Balance charges , if necessary, using subscripts.
Not balanced!
Al2S3

17. Criss-Cross Shortcut Method
Ex: Na+1 S2-
Na 2 S 1 = Na2S
sodium sulfide
Ex: Mg2+ Br-1
Mg1 Br2 = MgBr2
magnesium bromide

18. Chapter 7 SUTW Prompt
Describe the differences between writing chemical formulas for molecular compounds and ionic compounds.
Complete an 8-10 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink.
Due Date: Monday, October 31st, 2016 (start of class).