Oxidation Numbers 7-2

Beaker Breaker Name or write the formulas of the following acids: H 3 PO 4 = ___________ Nitric acid = _________ Hydrochloric acid ________ HBr =____________

In NaCl, Na is 1+ and Cl is 1- In H 2 O, what is the “value” (sign and number) of H and O? H is a +1 O is a -2 But………are these really “charges” ???? Are H and O “ions” in water ? Is H 2 O an ionically-bound compound? NO, NO and NO !!! These are oxidation numbers written as +1 and -2, rather than 1+ and 2-(charges)

Oxidation number also known as oxidation state number assigned to an atom in a molecular cmpd that indicates that general distribution of electrons among the bonded atoms gives an insight into the combining ability of an atom – not “real” charges but are artificial “bookkeeping” devices to keep track of overall e - distribution Ionic cmpds: the charge on the ion IS the electron distribution ∴ ox. # = charge on ion…physically meaningful info

Summary of Ox # Rules (p.216) 1.Pure elements have an ox. # of ZERO i.e. copper, Cu = ox # of zero oxygen, O 2 = ox # of zero 2. More electroneg. element has an ox. # = charge it would have if it were an anion. Less electroneg. element has an ox # = charge it would have if it were a cation.

3.F: -1 oxidation # 4.O: -2 oxidation # except in peroxide (H 2 O 2 ) where it is –1, and with halogens (OF 2 ) where it is H: +1 except when it’s more electroneg. than other atoms (metals….NaH) where it is –1. 6.Algebraic sum of all ox. #s in cmpd = 0. 7.Algebraic sum of all ox. #s in polyatomic ion = charge on ion. 8.IF ionic, ox. # = charge of the ion

Assign ox. #s to each element in the following cmpds or ions: CCl 4 NO 2 LiH sulfate ion nitrate ion H 3 PO 4 P 4 O 10

CCl 4 +4, -1 NO 2 +4, -2 LiH +1, -1 sulfate ion SO , -2 nitrate ion NO , -2 H 3 PO 4 +1, +5, -2 P 4 O 10 +5, -2

Using the newer Stock system, write formulas for the following molecular cmpds: nitrogen (II) oxide phosphorus (III) chloride sulfur (IV) oxide bromine

nitrogen (II) oxide NO phosphorus (III) chloride PCl 3 sulfur (IV) oxide SO 2 bromine Br 2

What would the previous molecular cmpds be names using the prefix system? NO nitrogen monoxide PCl 3 phosphorus trichloride SO 2 sulfur dioxide Br 2 bromine Br 2

Beaker Breaker Determine the oxidation numbers of the following: CaO =_________ CH 4 = _________ H 2 SO 4 =___________