Chapter 20, Problem 20.7QP

Interpretation Introduction

Interpretation: Reason for the first-row transition metals from left to right, the $+2$ oxidation state becomes more stable in comparison with the $+3$  state has to be explained.

Concept Introduction:

Transition elements contain either d subshell which are incomplete or that can form cations having incomplete d subshell.

First-row transition metals have outer electronic configurations of ${\text{3d}}^{\text{(1-10)}}{\text{4s}}^{\left(\text{1-2}\right)}$. The 4s orbitals have lower energy comparing to the 3d orbitals and are filled first

Third ionization energy: The minimum energy needed to remove an electron from a dipositive gaseous ion to form a tripositive ion in the ground state is known as third ionization energy.