InterviewSolution
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InterviewSolution
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(a) Account for the following : (i) Transition metals form large number of complex compounds. (ii) The lowest oxide of transition metal is basic whereas the highest oxide is amphoteric or acidic. (iii) E^(@) value for the Mn^(3+)//Mn^(2+) couple is highly positive (+1.57 V) as compare to Cr^(3+)//Cr^(2+). (b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements. |
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Answer» Solution :(a) (i) Transition metals from a large number of complex compounds due to comparatively smaller sizes of metal ions, their high ionic charges and the availability of d-orbitals for bond formation. (ii) As we move from lowest oxide to the highest oxide, the lone pair of electrons on the metal decrease. Basicity of a substance depends upon the number of free electrons AVAILABLE for donation. THEREFORE lowest oxide of transition metal is BASIC and the highest oxide is amphoteric or acidic. (iii) `Mn^(3+)//Mn^(2+)` couple has positive `E^(@)` value because from `Mn^(3+)` to `Mn^(2+)` involves change of configuration to half-filled `d^(5)` which has extra stability. `Cr^(3+)//Cr^(2+)` couple has negative `E^(0)` value because `Cr^(3+)` has stable half-filled `(t_(2g))` configuration and `Cr^(2+)` has `d^(4)` configuration which is relatively unstable and hence negative `E^(@)` value. (b) Lanthanoid and ACTINOID elements Similarity - Both lanthanoid and actinoid involve filling of electrons in the inner shells. Both are inner transition elements. Difference - Ionisation enthalpies of earlier actinoids are LOWER than those of early lanthanoids. |
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