Transition elements are usually characterised by variable oxidation states,but $Zn$ does not show this property because of:

Write a note on interstitial compounds.

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 of the following elements does not exhibit variable valency?

In which of the following,the tendency towards the formation of coloured ions is maximum?

In the first transition series,the metallic bond strength increases from ..... to .....