Account for the following statements :
(i) Co (ii) is stable in aqueous solution but in the presence of strong ligands and air it can get oxidised to Co (III) (at. No Co=27)
(ii) of the `d^4` species Cr (II) is strongly reducing but Mn (III) is strongly oxidising
(at. no Cr= 24 , Mn = 25, Co = 27)

How and you account for the following : (i) Cabalt (II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised. (ii) The transition elements exhibit high enthalpy of atomization. (iii) of the d^4 species, Cr^(2+) is strongly reducing while Mn (III) is strongly oxidsing .

Account for the following (i) Co(II) is stable in aqueous solution but in the presence of strong ligand and air , it can get oxidized to Co(III) . (ii) [Ni(CN)_(4)]^(2-) is square planar and diamagnetic whereas [NiCl_(4)]^(2-) is tetrahedral and paramagnetic .

Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents ( strong field ligands ) it is readily oxidised. Why ?

The pair having the same magnetic moment is [at. No. Cr = 24, Mn = 25, Fe = 26 " and " Co = 27]

The pair having the same magnetic moment is [at. No. Cr = 24, Mn = 25, Fe = 26 " and " Co = 27]

Give reasons for the following: (i) Transition metals exhibit a wide range of oxidation states. (ii) Cobalt (II) is very stable in aqueous solutions but gets easily oxidised in the presence of strong ligands. (iii) Actinoids exhibit a greater range of oxidation states than lanthanoids.

How would you account for the following : (i) Out of the d^(4) species, Cr^(2+) is strongly reducing while manganese (III) is strongly oxidising. (ii) Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidized. (iii) The d^(1) configuration is very unstable in ions.

(a) What is meant by the term lanthanoid contraction ? What is it due to and what consequences does it have on the chemistry of elements following lanthanoids in the periodic table ? (b) Explain the following observations : (i) Cu^(+) ion is unstable in aqueous solutions . (ii) Although Co^(2+) ion appears to be stable , it is easily oxidised to Co^(3+) ion in the presence of a strong ligand. (iii) The E_(Mn^(2+)//Mn)^(@) value for manganese is much more than expected from the trend for other elements in the series.

State the reason for the following : (i) Cu (I) ion is not stable in an aqueous solution. (ii) Unlike Cr^(3+),Mn^(2+),Fe^(3+) and the subsequent other M^(2+) ions of the 3d series, the 4d and 5d series metals generally do not form stable oxidation states.

How would you account for the following: A) Of the d^(4) species Cr^(2+) is strongly reducing while manganese(III) is strongly oxidizing. B) Cobalt(II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidized. C) The D^(1) configuration is very unstable in ions.