1. Ionic Formulas Rule of Eight
-ionic compounds (metal and nonmetal) tend to have atoms that together have a total of 8, 16, or 24 valence electrons which makes them similar to a noble gas which is very stable
Examples:
If the valence electrons add up to eight, leave as is. To combine Na and Br:
Na = 1 e- and Br = 7 e-  NaBr = 8 e-
If they don’t, change the number of each element until you get 8, 16, or 24. To combine Be and F:
Be = 2 e- and F = 7 e- mulitply F x 2.
Be = 2 e- and F (x2) = 14 e-  BeF2 = 16 e-

2. Ionic Formulas
Nobel gases are an exception. They already have 8 valence electrons, so they are happy the way that they are. =

3. Ionic Formulas metals: Na+ or Mg2+ nonmetals: O2- or F- Ions
-metals give up electrons  CATIONS
-nonmetals take electrons  ANION
-when metals give up valence electrons, they are left with a slightly positive charge
-when nonmetals take valence electrons, they are left with a slightly negative charge
For example:
metals: Na+ or Mg2+
nonmetals: O2- or F-

4. Ionic Formulas Na+ + F- = NaF and total charge = 0
-when combining metals and nonmetals, total charge should equal zero!
-if combining them doesn’t equal zero, change the number of atoms
For example:
To combine Na and F:
Na+ + F- = NaF and total charge = 0
To combine Na and O:
Na+ + O2- =  NO GOOD!
Na+ (x 2) + O2- = Na2O
and total charge = 0

5. Ions and Ionic Bond Practice
1. Write down the name of two ions/polyatomic ions that have a 1+ charge. How many electrons have they gained or lost?
2. Write down the name of two ions/polyatomic ions that have a 2- charge. How many electrons have they gained or lost?
3. Write down the name of two elements that will always have a 0 charge. How many electrons do they gain or lose?
Put together the following monatomic ions into compounds.
4. Ca and O
5. Ba and F
6. K and N
7. Mg and P
8. Li and Cl