(a) Account for the following :
(i) Copper(I) compounds are white whereas Copper(II) compounds are coloured.
(ii) Chromates change their colour when kept in an acidic solution.
(iii) Zn,Cd, Hg are considered as d-block elements but not as transition elements.

(b) Calculate the spin only moment of `Co^(2+)``(Z=27)` by writing the electronic configuration of `Co` and `Co^(2+)`

(a) Give reasons for the following : (i) Compounds of transition elements are generally coloured. (ii) MnO is basic while Mn_(2)O_(7) acidic. (b) Calculate the magnetic moment of a divalent ion squeous medium of its atomic number is 26.

(a) Account for the following : (i) Cu^(+) is unstable in an aqueous solution. (ii) Transition metals form complex compounds. (b) Complete the following equation: Cr_(2)O_(7)^(2-)+8H^(+)+3NO_(2)^(-)rarr

Explain the following observations: (i) Transition elements are known to form many interstitial compounds.. (ii) With the same d^4 configuration Cr^(2+) ion is reducing while Mn^(3+) ion is oxidising. (iii) The enthalpies of atomization of the transition elements are quite high.

How would you account for the following : (i) Among lanthanoids , Ln(III) compounds are predominant , However, occasionally in solutions or in solid compounds , +2 and +4 ions are also obtained . (ii) The E_(M2+//M)^(@) for copper is positive (0.34V ) . Copper is the only metal in the first series of transition elements showing this behaviour . (iii) The metallic radii of the third (5d) series of transition metals are nearly the same as those of the corresponding members of the second series .

Assign reasons for each of the following : (i) Transiti9n metals generally form coloured compounds. (ii) Manganese exhibits the highest oxidation state of+ 7 among the 3d series of transition elements.

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 .

Give reasons for the following: (i) Transition elements and their compounds act as catalysts (ii) E^(@) value for (Mn^(2+) | Mn) is negative whereas for (Cu^(2+) | Cu) is positive. (iii) Actinoids show irregularities in their electronic configuration.

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 .

(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 (+1.57V) as compare to Cr^(3+)//Cr^(2+) (b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

Explain the following observations : (i) Copper atom has completely field d orbitals (3d^(10)) in its ground state, it is regarded as a transition element. (ii) Cr^(2+) is a stronger reducing agent than Fe^(2+) in aqueous solutions.