(a) Given below the following characteristics of the first series of the transition metals and their trends in the series (Sc to Zn):
(i) Atomic radii
(ii) Oxidation status
(iii) Ionisation enthalpies
(b) Name an important alloy which contains some of the lanthanoid metals. Mention its two uses.

Calculate the number of unpaired electrons in following gaseous ions: Mn³⁺, Cr³⁺, V³⁺ and Ti³⁺. Which one of these is the most stable in aqueous solution?

Compare the general characteristics of the first series of the transition metals with those of the second and third columns. Give special emphasis on the following points:
(i) electronic configurations,
(ii) oxidation states,
(iii) ionisation enthalpies and 
(iv) atomic sizes.

(a) Out of Ag₂SO₄, CuF₂, MgF₂ and CuCI, which compound will be coloured and why?
(b) Explain :
(i) \({ CrO }_{ 4 }^{ 2- }\) is a strong oxidizing agent while \({ MnO }_{ 4 }^{ 2- }\) is not.
(ii) Zr and Hf have identical sizes.
(iii) The lowest oxidation state of manganese is basic while the highest is acidic.
(iv) Mn (II) shows maximum paramagnetic character amongst the divalent ions of the first transition series.

Complete the following chemical reaction equations:
(i) \(CrO_{ 7 }^{ 2\quad - }(aq)+H_{ 2 }S(g)+H^{ + }(aq)\longrightarrow \) 
(ii) \(CrO_{ 7 }^{ 2\quad - }(aq)+H_{ 2 }S(g)+H^{ + }(aq)\longrightarrow \)
(b) Explain the following observations:
(i) Transition metals form compounds which are usually coloured.
(ii) Transition metals exhibit variable oxidation states.
(iii) The actinoids exhibit a greater range of oxidation states than the lanthanoids.

(a) Give the preparation of potassium dichromate from chromate ore:
(b) Explain the following:
(i) Transition metals have good tendency to form complexes.
(ii) Transition metals exhibit variable oxidation states.
(c) Write the general electronic configuration of lanthanoids.

Gas (A) and gas (B) both turn K₂Cr₂O₇ /H⁺ green. Gas (A) also turn lead acetate paper black. When gas (A) is passed into gas (B)in an aqueous solution, yellowish white turbidity appears. Identify gas (A) and gas (B). Explain reactions also.

Explain the following observations:
(a) The transition metal ions are usually coloured in aqueous solutions.
(b) Cu(I) ion is not stable in an aqueous solution.
(c) The highest oxidation state of a transition metal is exhibited in its oxide or fluoride

Account for the following :
(a) Transition metals show variable oxidation states.
(b) Zn, Cd and Hg are soft metals
(c) E^o value for the Mn³⁺ /Mn²⁺ couple is highly positive (+ 1.57 V) as compared to Cr³⁺ /Cr²⁺.
(ii) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

(i) (a) How is the variability in oxidation states of transition metals different from that of the p-block elements?
(b) Out of Cu⁺ and Cu²⁺, which ion is unstable in aqueous solution and why?
(c) Orange colour of Cr₂O₇^2- ion changes to yellow when treated with, an alkali. Why?
(ii) Chemistry of actinoids is complicated as compared to lanthanoids. Give two reasons.