1. Ion Formation

2. Atoms Atoms are neutral
Atoms have the same number of protons (+) and electrons (-)
When atoms gain or lose electrons, they become electrically charged, and are called ions

3. Ions All atoms want to have a full outer electron shell (valence).
Atoms will gain or lose electrons to achieve a full valence.
The number of protons (+) is no longer equal to the number of electrons (-).
E.g.: Sodium now has 11 protons (+) and only 10 electrons (-) giving it an overall charge of 1+

4. Note: metals tend to LOSE ELECTRONS and become POSITIVE
Non metals tend to GAIN ELECTRONS and become NEGATIVE
The “ion charge” is the element’s most COMMON ION CHARGE, it is possible for it to have different charges

5. Ions
Metals tend to lose electrons to become postive ions (cations). +
1e- lost
Lithium
Lithium ion (Li+)
Non-metals tend to gain electrons to become negative ions (anions). -2
2e- gained
Oxygen
Oxygen ion (O2-)

7. What the charges mean…
Some metals are multivalent (can form ions in more than one way)
i.e.: Iron can lose 2 or 3 electrons to become a 2+ or 3+ ion.
On your periodic table, the most common charge is listed on top.
Ion Charges
Most Common Ion Charges

8. Practice! Complete this table: Symbol Atomic # Mass # Ion charge
# protons
# neutrons
# electrons B 5 11 1- Ca 20 40 18 47 1+ 61 56 26 27

9. Answers! Symbol Atomic # Mass # Ion charge # protons # neutrons
# electrons B 5 11 1- 6 Ca 20 40 2+ 18 Ag 47
108 1+ 61
107 Fe 26 56 30 27