Chapter 20: LEO the lion goes GER OXIDATION AND REDUCTION REACTIONS

RULES FOR ASSIGNING OXIDATION NUMBERS 1. EQUAL TO IONIC CHARGE EX: NaCl = Na+1 Cl-1 Except in H2O2 (H+1 and O-1) 2. HYDROGEN IS ALMOST ALWAYS +1 EXCEPT ALKALI METALS-HYDRIDES (NaH, LiH) 3. OXIDATION # OF AN UNCOMBINED ELEMENT IS ALWAYS ZERO EX: Mg = Mg0

RULES FOR ASSIGNING OXIDATION NUMBERS 4. SUM OF ALL OXIDATION #S MUST EQUAL ZERO IN A COMPOUND EX: NH3 = N-3 H3+1 FOR POLYATOMIC IONS, OXID. # MUST = THE CHARGE OF THE ION EX: (SO4)-2 = S+6 O4-2 (+6)+ -8 = -2

LEO the lion …… Oxidation: the combination of an element with oxygen (gain of oxygen). EX: 4 Fe(s) + 3O2(g) 2Fe2O3(s) Iron lost electrons = oxidized EX: Mg + S MgS Substance that loses e-s is the Reducing Agent (reducing in size b/c of loss of electrons) +3 -2 +2 -2

Oxidized = Reducing Agent The substance that is oxidized is the reducing agent Mg + S MgS Mg is OXIDIZED +2 Reducing Agent

……goes GER Reduction: the loss of oxygen EX: 2Fe2O3(s) + 3C(s) 4Fe(s) + 3CO2(g) Fe gains electrons =reduced EX: Mg + S MgS Substance that accepts e-s is an Oxidizing Agent +4 -2 +3 -2 +2 -2

Reduced = Oxidizing Agent The substance that is reduced is the oxidizing agent Mg + S MgS S is REDUCED -2 Oxidizing Agent