Question

Give explanation for each of the following observations:
(a) With the same d$^8$ orbital configuration, Mn$^{2+}$ ion is an oxidizing agent whereas Cr$^{2+}$ ion is a reducing agent.
(b) Atomic contraction is greater from element to element than much from lanthanides.
(c) Transition metals form large number of interstitial compounds with H, B, C, and N.

Hint:

When studying transition metals, focus on their electronic configurations, which help explain their ability to form interstitial compounds and act as both oxidizing and reducing agents.

Answer 1

(a) Mn$^{2+}$ functions as an oxidizing agent because it readily oxidizes to Mn$^{3+}$, a more potent oxidizing agent. Conversely, Cr$^{2+}$ acts as a reducing agent, easily oxidizing to the more stable Cr$^{3+}$.
(b) The significant atomic contraction observed across periods arises from the escalating nuclear charge, which draws electrons nearer the nucleus. Lanthanides, however, show minimal contraction owing to the shielding effect of f-orbitals.
(c) Transition metals can form interstitial compounds due to their compact atomic dimensions and the availability of void spaces between metal atoms, which accommodate small atoms such as H, B, C, and N.