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

Color in aqueous solutions for ions is determined by their electronic configuration and the presence of unpaired electrons. This phenomenon, primarily involving d-orbital electronic transitions, is characteristic of transition metal ions with unpaired electrons.

Analysis of each ion:

• Ti³⁺: Electronic configuration is [Ar] 3d¹. The single unpaired electron permits d-d transitions, resulting in a colored solution.
• Nb³⁺: Configuration is [Kr] 4d². Two unpaired electrons enable d-d transitions, thus producing color.
• Cu⁺: Electronic configuration is [Ar] 3d¹⁰. All d-orbitals are filled with paired electrons, preventing d-d transitions and making the ion colorless.
• Y³⁺: Configuration is [Kr]. The absence of d-electrons precludes d-d transitions, rendering the ion colorless.

Consequently, only Ti³⁺ and Nb³⁺ are colored in aqueous solutions due to unpaired electrons facilitating d-d transitions.

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