Question

\([\text{Ti(H}_{2}\text{O)}_{6}]^{2+}\) is a colored compound where as \([\text{Zn(H}_{2}\text{O)}_{6}]^{2+}\) is colorless, because

• A. Titanium has completely filled 3d orbitals and Zinc has partially filled 3d orbitals.
• B. Zinc has completely filled 3d orbitals and Titanium has partially filled 3d orbitals.
• C. Zinc has completely filled 4d orbitals.
• D. Titanium has completely filled 4d orbitals.

Hint:

Colour needs d-d transitions, which are possible only when the d subshell is partly filled.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Colour in transition metal complexes arises from d-d transitions.
These need a partly filled d subshell with room for an electron to move between split d levels.

Step 2: Electronic configurations
\(\text{Ti}^{2+}\) (Z = 22) is \([\text{Ar}]3d^{2}\), so the 3d subshell is partly filled and visible light is absorbed.
\(\text{Zn}^{2+}\) (Z = 30) is \([\text{Ar}]3d^{10}\), so the 3d subshell is completely filled and no d-d transition is possible.

Step 3: Compare the options
Options (C) and (D) talk about 4d orbitals, which are not involved here.
Option (A) reverses the facts.
Option (B) is the correct statement.

Final Answer:
The zinc ion has a completely filled 3d subshell while titanium has a partly filled one, option (B). \[ \boxed{\text{(B) }\text{Zinc has completely filled 3d orbitals and Titanium has partially filled 3d orbitals.}} \]