Misch metal is an alloy of $:-$

An element of the $3d-$ transition series shows two oxidation states $x$ and $y$,which differ by two units. Then:

The aqueous solution containing which one of the following ions will be colourless?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$. Assertion $(A)$: In aqueous solutions $Cr^{2+}$ is reducing while $Mn^{3+}$ is oxidising in nature.
Reason $(R)$: Extra stability to half-filled electronic configuration is observed than incompletely filled electronic configuration.
In the light of the above statement,choose the most appropriate answer from the options given below:

Which property from the following is $NOT$ exhibited by interstitial compounds?

If the colours of salts of transition elements are due to the presence of unpaired electrons in the transition metal ions,which of the following ions will be colourless in aqueous solution? (The atomic numbers of $Ti$ and $Fe$ are $22$ and $26$ respectively.)