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InterviewSolution
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How would you account for the following? (i) The atomic radii of the metals of the third`(5d)` series of transition elements are virtually the same as those of the corresponding member of the second `(4d)` serie (ii) The `E^(@)` value for the `Mn^(3+)//Mn^(2+)` couple is much more positive than that for `Cr^(3+)//Cr^(2+)` couple of `Fe^(3+)//Fe^(2+)` couple. (iii) The highest oxidation state of a metal is exhibited in its oxides or fluoride. |
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Answer» Correct Answer - (i) In the second transition series , the number of shells increases and so does the atomic size. However , in the third series `(5d series)` , the atomic size is more or loss the same . This is known as lanthanide contraction. This Is due to the poor shielding effect by f-electrons. (ii) The large positive `E^(@)` value for `Mn^(3+)//Mn^(2+)` show that `Mn^(2+)` is much more stable than `Mn^(3+)` . This is because of the fact that `Mn^(2+)` has `3d^(5)` configuration. This means that the d-orbital is half -filled . Half -filled and fully-filled configuration are very stable. Thus , the third ionization energy of `Mn` will be very high. (iii) Oxygen and fluorine act as strong oxidising agents from various metals . In other words, a metal exhibits highest oxidation state in its oxides and fluorides. For example , in `OsF_(6)` and `V_(2)O_(5)`, the oxidation states of `Os` and `V` are `+6` and `+5` respectively. |
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