Question

Which ion is colorless?
A. $C{{r}^{4+}}$
B. $S{{i}^{3+}}$
C. $T{{i}^{3+}}$
D. ${{V}^{3+}}$

Answer 1

Hint: Ions are an atom or group of atoms where the number of electrons is not equal to the number of protons. Ions are formed by the loss and gain of electrons by an atom. Cation (carried positive charged) and anion (carried negative charged) is the type of ions.

Complete step by step answer:
First we will discuss about the colored or colorless ions which is given in the question,
Colored ions: - Complex ions carrying transition metals and a number of unpaired electrons in the valence shell are colored ions. They are diamagnetic in nature and partially filled d-orbital elements are involved to generate the color.
Colorless ions: - Complex ions carrying non-transition metals and a number of paired electrons in their valence shell are colorless ions. They are paramagnetic in nature. And also fully filled d-orbital elements are not involved to generate colour so they are colorless.
Now we will discuss about the elements which is given in the question,
$
  \left( A \right)Cr\left[ Ar \right]3{{d}^{5}}4{{s}^{1}} \\
 C{{r}^{+4}}=\left[ Ar \right]3{{d}^{2}} \\
$
Two unpaired electrons→ paramagnetic
$
  \left( B \right)Sc=\left[ Ar \right]3{{d}^{1}}4{{s}^{2}} \\
 S{{c}^{+3}}=\left[ Ar \right]3{{d}^{2}} \\
$
Zero unpaired electrons→ diamagnetic
$
  \left( C \right)Ti=\left[ Ar \right]3{{d}^{2}}4{{s}^{2}} \\
 T{{i}^{+3}}=\left[ Ar \right]3{{d}^{1}} \\
$
One unpaired electrons→ paramagnetic
$
  \left( D \right)V=\left[ Ar \right]3{{d}^{3}}4{{s}^{2}} \\
 {{V}^{+3}}=\left[ Ar \right]3{{d}^{2}} \\
$
Two unpaired electrons →paramagnetic
Ions carrying a number of unpaired electrons or have partially filled or incomplete d-orbital, show colour in the aqueous solution. These are known as paramagnetic ions and the ions carrying a number of paired electrons and have fully or completely filled d-orbital do not show colour in the aqueous solution. These are known as diamagnetic ions.

So, the correct answer is Option B.

Note: The color of transition elements or metal is due to the number of partially filled or incomplete d-orbital when the transition elements or metal are completely or fully filled d-orbitals, they are colorless ions. They showed colour when visible light is absorbed