Topic: Intro to Redox: Assigning Oxidation Number Do Now: What is oxidation number for the following Metals in the ionic compounds below 1.Fe 2 O 3 2.FeO 3.AgCl 4.K 2 S 5.Mn 2 O 7

Redox Reactions = oxidation-reduction reaction Electrons transferred from 1 atom to another Redox reactions: – All single-replacement rxns – All combustion rxns Double Replace is never Redox

OIL RIG - memorize O – Oxidation I - is L - loss of electron R - Reduction I - is G – gain of electron

REDOX Oxidation & Reduction reactions are complementary reactions Something is oxidized - __________ electrons While something is reduced - ________ electrons They occur every day – Respiration – Photosynthesis – combustion loses gains

To understand these Redox Rxns we must first understand Oxidation numbers Rules to Assigning Oxidation Numbers ( oxidation # =what an atoms charge would be if it owned all it’s electron exclusively (not sharing)

#1: individual atom (monatomic, diatomic, polyatomic, but only 1 type of atom) = 0

#2 for an ion oxidation number = charge Ca +2 = +2 Cl -1 = -1 Al +3 = +3

# 3 When Fluorine is in a compound F is always ____________ CF 4 C= ___ F = _-1_ OF 2 O= ___ F = _-1_ +4 +2

# 4 When in a Oxygen is in a compound, O is AMLOST always ________ – EXCEPT when with Fluorine OF 2 O= _ ___ F = _-1_ – Except when O 2 is bonded with group 1 or 2 metal Then it’s a ____________________ – K 2 O 2 = K = ____O = ____ -2 Peroxide Don’t forget O 2 by itself has an oxidation number of 0

#5 H is nearly always + 1 except if bonded to metal then - 1 H 2 O H 2 O H = ____O = ____ H 2 SO 4 H 2 SO 4 H = ____SO 4 = ____ LiH LiH Li = ____H = ____ CaH 2 CaH 2 Ca = ____H = ____ NH 3 NH 3 N = ____H = ____

#6 For neutral compounds, sum of oxidation numbers = 0 H 2 O 2 H 2 O 2H = +1 = +2 1O= -2 = =0 H 2 SO 4 2 H 2 SO 4 2H = +1 = +2 1SO 4 = -2 = =0 LiH 1Li LiH 1Li = +1 = +1 1H= -1 = =0 CaH 2 1Ca CaH 2 1Ca = +2 = +2 2H= -1 = =0

#7 For polyatomic ions, sum of oxidation numbers = charge of ion SO SO S = ___= ___ 4O= ___ = ____ ___ + ___ =-2 NO NO N = ___= ___ 3O= ___ = ____ ___ + ___ =

# 8 If covalent compound – both elements are nonmetal, like to gain electrons (both negative?! – NO) – Assign negative to the more electronegative element – SiCl 4 : Si = +4, Cl = -1

Assign Oxidation #’s KCl CaBr 2 CO CO 2 Al(NO 3 ) 3 Na 3 PO 4 H 2 S NH 4 +1 SO 3 -2 K = +1, Cl = -1 Ca = +2, Br = -1 C = +2, O = -2 C = +4, O = -2 Al = +3, O = -2, N = +5 Na = +1, O = -2, P = +5 H = +1, S = -2 N = -3, H = +1 S = +4, O = -2