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L.YADAV PGT (CHEMISTRY) KV C.O.D JABALPUR

L.YADAV PGT (CHEMISTRY) KV C.O.D JABALPUR. FRACTIONAL OXIDATION NUMBER. DETERMINATION OF OXIDATION NUMBER. (a) Oxidation number of an element IN ITS PURE STATE is zero. For example- H 2 , S 8 , P 4 , O 3 (b) IN COMBINED STATE-

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L.YADAV PGT (CHEMISTRY) KV C.O.D JABALPUR

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  1. L.YADAVPGT (CHEMISTRY) KV C.O.D JABALPUR FRACTIONAL OXIDATION NUMBER

  2. DETERMINATION OF OXIDATION NUMBER (a) Oxidation number of an elementIN ITS PURE STATE is zero. For example- H2 , S8, P4 , O3 (b) IN COMBINED STATE- Oxidation number of ‘F’ is always -1. Oxidation number of ‘O’ is -2. EXCEPTION- in peroxides it is -1 and in super oxides it is -1/2 Oxidation number of alkali metal is always +1 oxidation number of ‘H’ is -1 in metal hydrides and +1 in non-metal hydrides. Oxidation number of alkaline metal is always +2 (c) Total oxidation number of a molecule is zero and total oxidation number of an ion is equal to its charge. (d) Maximum oxidation number of an element is equal to its group number.

  3. FRACTIONAL OXIDATION NUMBER It is the average oxidation state of an element when two or more of its atoms are present in different oxidation states in a given compound. It is determine with the help ofbond structure method. RULES FOR DETERMING THE OXIDATION NUMBER BY BOND STRUCTURE METHOD For a single covalent bond oxidation number is 1 unit i.e. For the most electropositive element it is +1 and for the more electronegative element it is -1 for a double covalent bond oxidation number is 2 unit i.e for the more electronegative element it is -2 and for the more electropositive element it is +2 For a triple covalent bond oxidation number is unit 3 i.e. for the more electropositive element it is +3 and for the most electronegative element it is -3. for a co-ordinate bond oxidation number for more electronegative element is -2 and for the more electropositive element it is +2. but if the donor atom is more electronegative then the co-ordinate bond is not determined for the oxidation number.

  4. SOME EXAMPLES OF COMPOUNDS SHOWING FRACTIONAL OXIDATION NUMBERS 1.OXIDATION NUMBER OF CARBON IN CARBON SUBOXIDE +2 0 +2 AVERAGE OXIDATION NUMBER=2+0+2/3=4/3

  5. 2.OXIDATION NUMBER OF BROMINE IN TRIBROMOCTAOXIDE O O O Br Br Br O O O O O AVERAGE OXIDATION NUMBER=6+4+6/3=16/3

  6. 3. OXIDATION NUMBER OF SULPHUR IN SULPHUR TETRA THIONATE ION 0 0 +5 +5 0 0 AVERAGE OXIDATION NUMBER=5+0+0+5/4=10/4 OR 5/2

  7. 4.FERROUS IN FERROUS FERRIC OXIDE(MAGNETITE ) 2+3 2+3 2+2 AVERAGE OXIDATION NUMBER=2+3+3/3=8/3

  8. 5.OXIDATION NUMBER OF LEAD(Pb) IN Pb3O4 +2 +4 +2 AVERAGE OXIDATION NUMBER=4+2+2/3=8/3

  9. EXERCISE 1. DETERMINE THE OXIDATION NUMBER OF THE UNDERLINED ELEMENTS IN GIVEN COMPOUNDS 2.

  10. 3. 4.

  11. 5. 6. 7.

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