Explain giving reasons:

(i) Transition metals and their compounds generally exhibit a paramagnetic behaviour.

Complete the following chemical equations:



Or

State reasons for the following:

(i) Cu (I) ion is not stable in an aqueous solution.

(ii) Unlike Cr^3+, Mn^2+, Fe³⁺ and the subsequent other M²⁺ ions of the 3d series of elements, the 4d and the 5d series metals generally do not form stable cationic species.

(a) Complete the following equations :
(i) Cr₂O₇^2- + 2OH^- --->
(ii) MnO₄^- + 4H⁺ + 3e^- --->

(b) Account for the following :
(i) Zn is not considered as a transition element.
(ii) Transition metals form a large number of complexes.
(iii) The E° value for the Mn³⁺/Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺ couple.

OR

(i) With reference to structural variability and chemical reactivity, write the differences between lanthanoids and actinoids.

(ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
(iii) Complete the following equation :
MnO₄^- + 8H⁺ + 5e^---->
iv) Mn³⁺ is more paramagnetic than Cr³⁺.

Write the formula of an oxo-anion of Manganese (Mn) in which it shows the oxidation state equal to its group number.

355.

What happens when
(NH₄)₂Cr₂O₇ is heated?

Account for the following :
Transition metals form large number of complex compounds.

Account for the following :
The lowest oxide of transition metal is basic whereas the highest oxide is
amphoteric or acidic.

Account for the following :
E° value for the Mn³⁺/Mn²⁺ couple is highly positive (+1.57 V) as compared to Cr³⁺/Cr²⁺.

Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

Out of Cu⁺ and Cu²⁺, which ion is unstable in aqueous solution and why?