RULES OF OXIDATION NUMBER ASSIGNMENT STEPS IN ASSIGNNING OXIDATION NUMBERS 1) IF THE PERIODIC TABLE GIVES ONLY ONE OXIDATION STATE, USE THAT THAT STATE. EXAMPLE Zn+2 . 2) APPLY THE RULES OF THIS POWERPOINT TO SOLVE FOR OXIDATION NUMBERS OF ELEMENTS WITH MULTIPLE OXIDATION STATES. 3) IF A MULTIPLE OXIDATION STATE ELEMENT HAS NO RULE, ASSIGN IT A VARIABLE AND SOLVE USIMNG THE ALGEBRA RULE(SLIDE 3).

THE SUM OF THE OXIDATION NUMBER (STATE ) OF EACH ATOM IN A COMPOUND EQUALS THE CHARGE OF THAT COMPOUND. KMnO4 GIVEN: K IS +1(GROUP 1 RULE ), O IS -2 (OXYGEN RULE) Mn HAS MULTIPLE STATES(PERIODIC TABLE) +1 + X + 4(-2) = 0 ALGEBRA RULE EXAMPLES. Use group one to find other elements. note: caution with oxygen in binary compounds Li2O2 2(+1) + 2(X) = 0 X=O (oxygen) = -1 Use group one as a known for muli oxidation stare elements Na2SO4 2(+1) + (X) + 4(-2)= 0 X = S = +4 each S

GROUP ONE RULE EXAMPLES. GROUP ONE ELEMENTS ARE ALWAYS 1+ IN COMPOUNDS OR AS FREE (AQ) IONS. Ex in NaCl EACH Na has an oxidation state of 1+. in K2SO4 EACH K has an oxidation state of 1+. A Li+1 (aq) free ion has an oxidation number of 1+. GROUP ONE RULE EXAMPLES. Use group one as a known for muli oxidation stare elements. Na2SO4 2(+1) + (X) + 4(-2)= 0 X = S = +4 each S Use group one to find other elements. Li2O2 2(+1) + 2(X) = 0 X=O (oxygen) = -1 each

GROUP ONE RULE EXAMPLES. GROUP TWO ELEMENTS HAVE AN OXIDATION STATE OF 2+ IN COMPOUNDS AND AS FREE (AQ) IONS.   Ex in1) BaCl2 EACH Ba has an oxidation state of 2+ JJIBGO 2) In Ca3(PO4)2 EACH Ca has an oxidation state of 2+. A free Mg+2 ION (AQ) has an oxidation state of 2+.   GROUP ONE RULE EXAMPLES. Use group TWO as a known for muli oxidation stare elements. Ca3(PO4)2 3(+2) + 2(x) + 8(-2)=0 X = P = +6 each P Use group TWO to find other elements. BaO2 1(+2) + 2(X) = 0 X=O (oxygen) = -1 each

ALL UNCOMBINED NEUTRAL (ELEMENTAL STATE) ATOMS HAVE AN OXIDATION STATE OF 0. THE NONPOLAR COVALENT DIATOMOIC MOLECULES OF THE PERIODIC TABLE ALSO HAVE AN OX# OF 0. EX: Au0, Fe0, Na0, etc. EX: H2, O2, N2, Cl2, Br2, I2, F2 are3 all in the 0 oxidation state

THE OXIDATION NUMBER OF IONS IS THE IONIC CHARGE THE OXIDATION NUMBER OF IONS IS THE IONIC CHARGE. EX: Au+2 = 2+, Fe+3 = 3+, Na+ = 1+, etc. EX: NO3 - HAS AN OXIDATION NUMBER OF 1- FOR THE (EACH) POLY ATOMIC ION GROUP.

Fluorine is always 1- in its compounds THE OXYGEN RULES: Each oxygen USUALLY has an oxidation state of 2- in compounds, 0 in O2. EX, in H2O oxygen is 2- In H2SO4 EACH oxygen is 2- IMP -- EXCEPTION #1– when oxygen is contained in a PEROXIDE, it has an oxidation state of 1-. PEROXIDES - contain the peroxide ion (O2-2), EACH oxygen is 1-. - peroxides are when 2 group one elements combine with the peroxide ion H2O2, Li2O2, K2O2 are peroxides, each O is 1- BaO2, CaO2, MgO2 are peroxides, each O is 1- IMP -- EXCEPTION #2 – when oxygen is combined with FLOURINE, its oxidation state is 1+ or 2+. Fluorine is electronegative enough to oxidize oxygen. EXAMPLE : in FO the oxygen is +1, in F2O each oxygen is 2+ USE CAUTION IN BINARY COMPOUNDS OF OXYGEN AND HYDROGEN -- CHECK FOR RULE EXCEPTIONS. Fluorine is always 1- in its compounds

THE HYDROGEN RULE: THE OXIDATION STATE OF HYDROGEN IS USUALLY 1+   EX in H2O each hydrogen is 1+   IMP-EXCEPTION – in GROUP 1 METAL HYDRIDES the hydrogen is 1-, hydrogen is electronegative enough to oxidize group one metals. EX: NaH, KH etc the hydrogen is 1-   USE CAUTION IN BINARY COMPOUNDS OF OXYGEN AND HYDROGEN -- CHECK FOR RULE EXCEPTIONS.