Oxidation States

Oxidation State: the apparent charge that an atom would have if electron pairs in covalent bonds belonged entirely to the more electronegative atom Oxidation Number: positive or negative number assigned to an atom based on its oxidation state “Electron bookeeping”

Common Oxidation Numbers (p. 658) Atom or Ion Oxidation # Examples atoms in elements Fe, C, O2, F2 hydrogen +1 HCl, NH3 hydrogen with metals -1 NaH, CuH2 oxygen -2 H2O, FeO, NO3- oxygen in peroxides H2O2 monoatomic ions ion charge Mg2+, Na+, S2-

Determining Oxidation Numbers Assign common oxidation numbers The sum of oxidation numbers for a compound is 0 The sum of oxidation numbers for a polyatomic ion is its charge Use algebra to determine any unknown oxidation numbers Examples: K2SO4 K2Cr2O7 MnO4-

CH4(g) + 2O2(g)  CO2(g) + 2H2O(l) Redox Reactions Oxidation numbers change in a redox reaction Oxidation is an increase in oxidation number Reduction is a decrease in oxidation number Ca(s) + Cl2(g)  CaCl2(s) CH4(g) + 2O2(g)  CO2(g) + 2H2O(l)

Practice Oxidation States of Vanadium Activity p. 659 #12-14, 15a, 16, 17 p. 662 #18-20 p. 663 #1, 2, 5-8, 10