d-block elements have tendency for complex formation because of

Options

A. Small size of metal ions
B. High ionic charges
C. Availability of vacant d-orbitals
D. All of these

Answer

To answer the question regarding why d-block elements have a tendency for complex formation, we can break down the explanation into several key points:

### Step-by-Step Solution:

1. **Definition of d-block Elements**:
- d-block elements, also known as transition metals, are found in groups 3 to 12 of the periodic table. They include elements such as iron, copper, and nickel.

2. **Electronic Configuration**:
- Transition metals have partially filled d-orbitals. For example, the electronic configuration of Scandium (Sc) is [Ar] 3d¹ 4s². The presence of d-electrons is crucial for their chemical behavior.

3. **Vacant d-Orbitals**:
- One of the primary reasons for the complex formation tendency in d-block elements is the presence of vacant d-orbitals. These vacant orbitals can accept electron pairs from ligands (molecules or ions that can donate a pair of electrons).

4. **Coordination Number**:
- The ability of transition metals to form complexes is also influenced by their coordination number, which is determined by the number of ligands that can bond to the metal ion. This is facilitated by the availability of vacant d-orbitals.

5. **Small Size of Metal Ions**:
- Transition metals typically have a small ionic radius, which allows them to attract ligands more effectively. The small size increases the charge density, enhancing the metal's ability to form complexes.

6. **High Ionic Charges**:
- Transition metals can exhibit multiple oxidation states, leading to high ionic charges. This property also contributes to their ability to form stable complexes with various ligands.

### Conclusion:
The tendency of d-block elements to form complexes arises from the combination of vacant d-orbitals, small ionic size, and the ability to exhibit high ionic charges.