(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+)`

Account for the following: (i) Copper (I) compounds are white whereas Copper (II) compounds are coloured. (ii) Transition metals and their compounds show catalytic activities. (iii) Zn,Cd,Hg are considered as d-block elements but not as transition elements (iv) Transition metals and many of their compounds show paramagnetic behaviour. (v) Transition metals can form alloy.

Explain the following : (i) Cu^(+) is colourless and Cu^(2+) is coloured. (ii) Zn shows only +2 oxidation state it its compounds.

(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) What is Lanthanoid contration ? What are its important effects ? (b) Account for the following : (i) Zn^(2+) salts are white while Ni^(2+) salts are coloured. (ii) Ionisation enthalpies of 5d series elements are higher than the corresponding 3d series elements

(i) Account for the following : (a) White silver chloride turns grey in sunlight. (b) Brown coloured copper powder on heating in air turns into black coloured substance. (ii) What do you mean by (a) Displacement reaction (b) Reduction reaction (c) Combination reaction ? Write balanced chemical equation.

Explain the following : (i) Most of the transition elements show variable oxidation states. (ii) Most of the compounds of transition elements are coloured. (iii) Many transition elements and their compounds are paramagnetic .

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^@(M^(2+)| 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.