Topic Oxidation States and Criss Cross Method Do

Topic: Oxidation States and Criss Cross Method • Do Now: Ionic, Covalent or Metallic 1. 2. 3. 4. 5. Mg Mg. O Na. Cl CO 2 H 2 O 1. Metallic 2. Ionic 3. Ionic 4. Covalent 5. Covalent

Ionic bond is a bond between: positive ion and negative ion • Metals: lose valence electrons – form cation (+ ion) • Nonmetals: gain electrons – form anion (- ion)

• Metals lose their valence electrons and nonmetals gain

IONIC BONDING • Ionic compounds are electrically neutral overall 1 Ca = +2 x 1 = +2 2 Cl = -1 x 2 = -2 2 K = +1 x 2 = +2 1 S = -2 x 1 = -2 2 Cr = +3 x 2 = +6 3 O = -2 x 3 = -6

Assigning Oxidation States • You can look at your periodic table. It’s listed in the topic right corner. • What do you do if there is more then one? !

What to do if more then 1 oxidation state • VS 2 5 – Nonmetal = top number – So S would be -2 +5 -2 – V 2 S 5 ____ +5 x 2 = +10 -2 x 5 = -10 • Then determine the oxidation state of the metal that will give you the same number but positive

Criss-Cross Method Mg+2 and Cl-1 Crisscross and Drop Mg 1 Cl 2 but if subscript is 1, forget it! Mg. Cl 2 means 1 Mg+2 and 2 Cl-1

NOTE: The formula has to be in the simplest whole number ratio (this is called the empirical formular Be 2 O 2 = Be. O Al 3 N 3 = Al. N

Try a few formulas: • • Ca+2 + Cl-1 Na+1 + O-2 Cs+1 + S-2 Al+3 + Cl-1 Al+3 + Se-2 Mg+2 + F-1 Ca+2 + S-2 Ca. Cl 2 Na 2 O Cs 2 S Al. Cl 3 Al 2 Se 3 Mg. F 2 Ca. S