1. To learn how to write ions
OBJECTIVES
To learn how to write ions

2. Chemical Formula
There are two types of chemical formulas that we discuss
Molecular formulas – represent the numbers and kinds of atoms in a covalent molecule.
Formula units – represent the smallest whole number ratio of ions in an ionic compound
All formulas represent electrically neutral compounds

3. Ionic Compounds
The electrical attraction between a cation and an anion.
Metals lose electrons to form positive ions (cations)
Non-metals gain electrons to form negative ions (anions)
Both metals and non-metals want noble gas configuration.

4. Determine Charges
For most of the Main group elements, the Periodic Table can tell what kind of ion they will form from their location.
Main Group Metals will lose all of its valence electrons (groups 1, 2 & 3) to attain an octet
Mg 1s22s22p63s2
Mg s22s22p6

5. Determine Charges
Main Group Non-metals will gain enough electrons to form an octet
O 1s22s22p4
O s22s22p6

6. Determine Charges
Because we know that all atoms want to attain an octet and we know the number of valence electrons on each atom we can use this to determine how many electrons an atom is going to gain or lose.
Transition metals and Sn and Pb in column 14 don’t follow the typical pattern

7. +1 +4 +2 +2 +3 -3 -2 -1 +1 +2 +3 +4

8. Write Formulas for these cations
Ex: Potassium ion K+1
Magnesium ion
Aluminum ion
Sodium ion
Barium ion
Calcium ion

9. Write Formulas for these anions
Ex: Nitrogen ion N-3
Oxygen ion
Phosphorous ion
Bromine ion
Chlorine ion
Fluorine ion