In which one of the following species does the transition metal ion have d^3 electronic configuration?

To answer this question, we first need to understand what a d^3 electronic configuration means. In the context of transition metals, a d^3 configuration means that there are three electrons in the d orbital.

Transition metals are elements found in groups 3-12 of the periodic table and their ions can have a variety of different electron configurations. The electron configuration of an ion is determined by the number of electrons it has, which in turn is determined by its atomic number (the number of protons) and its charge (the number of extra or missing electrons).

To find a transition metal ion with a d^3 configuration, we need to look for an element that has three more electrons than protons when it is in its ionized state.

One example of such an element is Vanadium (V). In its neutral state, Vanadium has an atomic number of 23, which means it has 23 electrons. When it loses two electrons to form a +2 ion (V2+), it has 21 electrons. The electron configuration of V2+ is [Ar] 3d^3 4s^0. Therefore, V2+ is a transition metal ion with a d^3 electronic configuration.