1. Metal atoms lose e- to form positive ions called cations: K + Ca 2+ NH 4 + Nonmetal atoms gain e- to form negative ions called anions: Cl - S 2- CO 3 2- Mg 2+ Superscript written to the upper right shows the charge F-F- If the charge is +1 or -1, you don’t have to include the “1” Called an “oxidation number” Ion: An atom (or group of atoms) that has lost or gained e- to follow the Octet Rule and is now electrically charged

2. Ionization F + e -  F - Neutral but unstable fluorine atom, F Write the (oxidation) equation showing how magnesium becomes an ion Same # electrons as neon, but NOT an atom of neon! Mg  Mg 2+ + 2e - Same # e- as…which element? Write the (reduction) equation showing how flourine becomes an ion

3. 1A metals: +1 ions2A metals: +2 ions 7A nonmetals: -1 ions6A nonmetals: -2 ions What patterns do you see? Are there any exceptions to these patterns?

4. Nonmetal atoms remove e- from metal atoms. Ionic Bonds The two atoms become oppositely charged ions that attract each other, resulting in an ionic bond. An ionic compound forms. Na + Cl -

5. EX 2: Write the formula for the ionic compound calcium oxide Step 1: Write each ion with the correct charge. Look at periodic table group or cheat sheet for help. Ca 2+ O 2- Step 2: “Criss-cross” number associated with each charge (do not include the + or -) Ca 2 O 2 Step 3: Remove any subscripts of 1. Eliminate both subscripts if they are the same. Write the formula. CaO EX 3: Write the formula for the ionic compound aluminum Sulfide Al 3+ S 2- Al 2 S 3

6. Name  Formula potassium nitride Magnesium bromide potassium phosphide magnesium fluoride K3NK3N MgBr 2 K3PK3P MgF 2

7. Name these 2 compounds: CoS a.Figure out which ions form the compound because the ion charge could be important. Since S forms S 2-, Co must be Co 2+ b. Name the ions, cation first, then anion c. Change ending to –ide if it’s a pure element. cobalt (II)sulfide d. Transition metals always get a roman numeral to indicate their charge! Na 2 SO 3 sodium sulfite Common mistakes: sodium(II)sulfite sodium(I)sulfite sodium sulfide/sulfate

8. Formula  Name Na 2 O SrS LiBr RbCl Sodium Oxide Strontium Sulfide Lithium Bromide Rubidium Chloride