`[Sc (H_(2)O)_(6)]^(3+)` ion is :-

Options

A. Coloured and paramagnetic
B. Colourless and paramagnetic
C. Colourless and diamagnetic
D. Coloured & octahedral

Answer

To determine the properties of the ion \([Sc(H_2O)_6]^{3+}\), we will analyze its electronic configuration, magnetic properties, and geometry step by step.

### Step 1: Identify the Atomic Number and Electronic Configuration of Scandium
- Scandium (Sc) has an atomic number of 21.
- The electronic configuration of Sc is:
\[ \text{Sc: } [Ar] 3d^1 4s^2 \]

**Hint:** Remember that the electronic configuration helps us understand the distribution of electrons in different energy levels.

### Step 2: Determine the Electronic Configuration of Scandium Ion
- The ion \([Sc(H_2O)_6]^{3+}\) means that Scandium has lost 3 electrons.
- Removing 3 electrons from the configuration \([Ar] 3d^1 4s^2\) results in:
- The 2 electrons from the 4s subshell and 1 electron from the 3d subshell.
- Therefore, the electronic configuration of \([Sc]^{3+}\) is:
\[ \text{Sc}^{3+}: [Ar] 3d^0 4s^0 \]

**Hint:** When forming cations, electrons are removed from the outermost shell first.

### Step 3: Analyze the Magnetic Properties
- The configuration \([Ar] 3d^0 4s^0\) indicates that there are no unpaired electrons in the d subshell.
- Since there are no unpaired electrons, the ion is classified as **diamagnetic**.

**Hint:** Diamagnetic substances are those that have all their electrons paired and are not attracted to a magnetic field.

### Step 4: Determine the Color and Shape of the Complex
- The complex \([Sc(H_2O)_6]^{3+}\) has 6 water molecules acting as ligands, which means it has an octahedral geometry.
- The presence of 6 ligands and the absence of unpaired electrons typically results in the complex being **colorless**.

**Hint:** The color of a transition metal complex is often due to the presence of unpaired electrons and the type of ligands. In this case, the absence of unpaired electrons leads to a colorless complex.

### Conclusion
- The ion \([Sc(H_2O)_6]^{3+}\) is **diamagnetic** and **colorless**, and it has an **octahedral shape**.

**Final Answer:** The correct option is **C: Diamagnetic and Colorless**.