Question

Which of the following has the smallest ionic radius?

• A. Sc³⁺
• B. Ti³⁺
• C. V³⁺
• D. Cr³⁺

Hint:

When comparing ionic radii, remember that the charge of the ion plays a key role. Higher charges usually result in smaller ionic radii.

Answer 1

The Correct Option is A

Ionic radius tends to decrease as the charge on the ion increases, because the electrostatic attraction between the nucleus and the electrons becomes stronger, causing the electron cloud to contract. For transition metals in particular, the ionic radius decreases as the nuclear charge increases due to the increasing number of protons pulling the electrons closer to the nucleus. Comparing the ions: - Sc³⁺ (Scandium) has a +3 charge, and the electron configuration is [Ar], with only 18 electrons. The ion is highly contracted. - Ti³⁺ (Titanium) has a +3 charge with electron configuration [Ar], but it has a larger ionic radius than Sc³⁺ because of a greater number of protons pulling the electrons. - V³⁺ (Vanadium), Cr³⁺ (Chromium), and Mn³⁺ (Manganese) also have +3 charges but have slightly larger ionic radii as the nuclear charge increases compared to Sc³⁺. Thus, Sc³⁺ has the smallest ionic radius.