Find the correct matches.
| A. | $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$ | P. | is predominantly a basic compound. |
|---|---|---|---|
| B. | $\mathrm{FeCr}_2 \mathrm{O}_4$ | Q. | is predominantly a acidic compound |
| C. | $\mathrm{CrO}_3$ | R. | forms yellow chromate on reaction with $\mathrm{Na}_2 \mathrm{CO}_3$ in air. |
| D. | $\mathrm{CrO}$ | S. | is interconvertible with $\mathrm{MO}_4^{2-}$ depending on the pH of the medium. |
Choose the statements which are incorrect in the case of Lanthanoids.
A. $\mathrm{Ce}^{4+}$ is diamagnetic while $\mathrm{Sm}^{3+}$ is paramagnetic.
B. The atomic size of the transition metals having atomic number greater than 71 are very close to that of the elements above them.
C. Lanthanoids react with hot water forming water soluble $\mathrm{Ln}(\mathrm{OH})_3$ with the liberation of $\mathrm{O}_2$.
D. The general electronic configuration of Lanthanoids is $(n-2) \mathrm{f}^{1-14} 5 \mathrm{~d}^0 6 \mathrm{~s}^2$, where $n=6$.
Which is the correct order of increasing number of unpaired electrons in the following ions?
$$\mathrm{A}=\mathrm{Cr}^{2+}(\mathrm{Z}=24) \mathrm{B}=\mathrm{Cu}^{2+}(\mathrm{Z}=29) \quad \mathrm{C}=\mathrm{Ni}^{2+}(\mathrm{Z}=28) \mathrm{D}=\mathrm{Fe}^{3+}(\mathrm{Z}=26)$$