1. Ions

2. Remember…  Atomic Number is the number of protons in an atom.  The number of protons equal the number of electrons in a neutral atom.  Atomic Mass is the sum of the protons and neutrons in an atom.  6p + + 6n 0 = 12 (atomic mass of carbon)

3. All atoms want a full valence electron shell (outermost energy level).  Octet Rule: All atoms want 8 valence electrons.  Exceptions to the Octet Rule  Hydrogen and Helium  They follow the Duet Rule: 2 valance electrons.

4. Ions  A charged entity.  This occurs if the number of electrons do not equal the number of protons.  This only occurs when an electron is added or removed from an atom.  The number of protons never change. An atom will gain or lose electrons to become more stable.

5. Predicting the Ionic Charge  Figure the number of valence electrons of the atom.  If an atoms has 5 or more valence electrons…  It will gain electrons to get a total of 8 valence electrons.  If an atoms had 3 or less valence electrons…  It will lose electrons to go back to the previous full electron shell.  If an atom has 4 valence electrons it may lose or gain electrons to get a full valence shell.  Most atoms lose the 4 valence electrons.

6. PREDICTING ION CHARGES In general  metals (Mg) lose electrons ---> cations (Mg 2+ ) ons (F - )  nonmetals (F) gain electrons ---> anions (F - )

7. Cations  ion with a positive charge.  If a neutral atom loses one or more electron it becomes a cation. Na 11 protons 11 electrons Na + 11 protons 10 electrons

8. Anions  ion with a negative charge.  If a neutral atom gains one or more electrons it becomes an anion. Cl 17 protons 17 electrons Cl - 17 protons 18 electrons

9. How would you write the symbol for the sodium CATION? EXAMPLE Na + How many outer electrons does sodium have before it loses one? It has 1…remember the group number!

10. A monatomic ion contains only one atom A polyatomic ion contains more than one atom 2.5 Na +, Cl -, Ca 2+, O 2-, Al 3+, N 3- OH -, CN -, NH 4 +, NO 3 -

11. Oxidation State of Elements Se 2- Te 2- 1 2 3 4 5 6 1 2 3 4 5 6 Al 3+ Zn 2+ Ag 1+ N 3- O 2- F 1- Cl 1- S 2- Br 1- I 1- Period Be 2+ Na + K+K+ Rb + Cs + Ba 2+ H+H+ Li + Ca 2+ Sr 2+ Mg 2+ Group 1 2 13 14 15 16 17 18 NOBLEGASESNOBLEGASES Transition metals

12. Some Polyatomic Ions 2.7