What is/are the coordination number(s) of Au in the complexes formed by Au?

Options

A. 6
B. 4
C. 5
D. 2

Answer

To determine the coordination number(s) of gold (Au) in its complexes, we need to analyze its oxidation states and the resulting coordination geometries.

### Step-by-Step Solution:

1. **Understanding Coordination Number**:
- The coordination number is defined as the number of bonds formed between a central metal ion and the surrounding ligands. It indicates how many ligands are bonded to the metal ion.

2. **Identify the Common Oxidation States of Gold**:
- Gold primarily exhibits two oxidation states: +1 and +3. These oxidation states will influence the coordination number.

3. **Analyze the +1 Oxidation State (Au⁺)**:
- In the +1 oxidation state, gold loses one electron from its 5d orbital. The electronic configuration becomes 5d⁹.
- In this state, gold typically forms complexes with a coordination number of 2, which results in a linear geometry (sp hybridization).

4. **Analyze the +3 Oxidation State (Au³⁺)**:
- In the +3 oxidation state, gold loses two electrons (one from the 5d orbital and one from the 6s orbital). The electronic configuration becomes 5d⁸.
- In this state, gold usually forms complexes with a coordination number of 4, which leads to a square planar geometry (dsp² hybridization).

5. **Conclusion**:
- Therefore, the coordination numbers of gold in its complexes are:
- Coordination number 2 for Au⁺ (linear geometry).
- Coordination number 4 for Au³⁺ (square planar geometry).

### Final Answer:
The coordination numbers of Au in its complexes are 2 and 4.