Larger number of oxidation states are exhibited by the actinoids than those of lanthanoids. The reason is:

Which is the correct order of increasing number of unpaired electrons in the following ions?

$$\mathrm{A}=\mathrm{Cr}^{2+}(\mathrm{Z}=24) \mathrm{B}=\mathrm{Cu}^{2+}(\mathrm{Z}=29) \quad \mathrm{C}=\mathrm{Ni}^{2+}(\mathrm{Z}=28) \mathrm{D}=\mathrm{Fe}^{3+}(\mathrm{Z}=26)$$

Arrange the following ions in the decreasing order of covalent double bonds formed by the transition metal with oxygen.

A. $=$ chromate $\mathrm{B}=$ permanganate $\mathrm{C}=$ dichromate

Match the metals in Column II with their characteristic properties given in Column I.

	Properties		Metals
A.	Lanthanoid with low value of $3^{\text {rd }}$ ionisation enthalpy.	P	V
B.	f-Block element with electronic configuration $[R n] 6 d^2 7 s^2$	Q	Gd
C.	3 d -series metal whose $\mathrm{M}^{3+}{ }_{(\mathrm{aq})}$ is colourless.	R	Th
D.	3d-series metal with highest $\Delta \mathrm{H}_{\text {(atomisation) }}$	S	Sc