Question

Which of the following ions will be coloured in the aqueous solution?
(A) Ti³⁺
(B) Nb³⁺
(C) Cu⁺
(D) Y³⁺
Choose the correct answer from the options given below:

• A. (C) and (D) only
• B. (A), (B) and (D) only
• C. (A) and (B) only
• D. (A), (B), (C) and (D)

Answer 1

The Correct Option is C

To determine which ions will be colored in aqueous solution, we must understand the electronic configuration and the presence of unpaired electrons in these ions. Ions are colored due to electronic transitions between different energy levels, primarily within d-orbitals. This phenomenon occurs in transition metal ions where unpaired electrons are present.

Let's evaluate each ion:

• Ti³⁺: Titanium in the +3 oxidation state has the electronic configuration [Ar] 3d¹. The presence of 1 unpaired electron in the d-orbital makes it capable of d-d transitions, resulting in a colored solution.
• Nb³⁺: Niobium in the +3 oxidation state has the configuration [Kr] 4d². With 2 unpaired electrons, it can also undergo d-d transitions, therefore it will be colored.
• Cu⁺: Copper in the +1 oxidation state has the electronic configuration [Ar] 3d¹⁰. All d-orbitals are filled with paired electrons, precluding d-d transitions, and rendering the ion colorless.
• Y³⁺: Yttrium in the +3 oxidation state has the configuration [Kr]. With no d-electrons present, it lacks the ability for d-d transitions, making it colorless.

Therefore, only Ti³⁺ and Nb³⁺ exhibit color in aqueous solutions due to the presence of unpaired electrons allowing d-d transitions.

The correct answer is: (A) and (B) only

Answer 2

The color of ions in aqueous solutions depends on the presence of unpaired d-electrons in transition metal ions. These unpaired electrons can absorb certain wavelengths of light, leading to the color observed.

• (A) Ti³⁺: Titanium in the +3 oxidation state has an electronic configuration of 3d¹. The presence of an unpaired electron in the d-orbital allows it to absorb light, resulting in a colored solution.
• (B) Nb³⁺: Niobium in the +3 oxidation state has an electronic configuration of 4d¹. Similar to Ti³⁺, the unpaired electron in the d-orbital results in a colored solution.
• (C) Cu⁺: Copper in the +1 oxidation state has an electronic configuration of 3d¹⁰, which means there are no unpaired electrons. Therefore, Cu⁺ does not absorb visible light and does not exhibit color.
• (D) Y³⁺: Yttrium in the +3 oxidation state has an electronic configuration of 4d⁰. Since there are no d-electrons, Y³⁺ does not absorb visible light and is colorless in solution.

Only Ti³⁺ and Nb³⁺ are colored in aqueous solution because they have unpaired d-electrons.

Therefore, the correct answer is Option C: (A) and (B) only.