Which of the following species containing mercury is most toxic ?

Options

A. `CH_3Hg^(+)`
B. `HgCl_2`
C. `Hg_2Cl_2`
D. `Hg` metal.

Answer

To determine which species containing mercury is the most toxic, we need to analyze the different forms of mercury and their toxicity levels.

### Step-by-Step Solution:

1. **Identify the Forms of Mercury**:
Mercury exists in several forms, including elemental mercury (Hg), inorganic mercury (e.g., mercury chloride), and organic mercury compounds (e.g., methylmercury and ethylmercury).

2. **Understand the Toxicity of Mercury Forms**:
- **Elemental Mercury (Hg)**: While it can be toxic, it is less toxic than some of its compounds when inhaled or ingested.
- **Inorganic Mercury Compounds**: These can be toxic but are generally less toxic than organic mercury compounds.
- **Organic Mercury Compounds**: Methylmercury is known to be highly toxic and can bioaccumulate in the food chain, leading to severe health effects.

3. **Evaluate the Given Species**:
- The question mentions a specific species, CS3Hg+ (which is methylmercury). This is an organic form of mercury and is known for its high toxicity.

4. **Conclusion**:
Based on the analysis, methylmercury (CS3Hg+) is the most toxic species containing mercury. Therefore, the correct answer is **Option 1: CS3Hg+**.

### Final Answer:
The most toxic species containing mercury is **CS3Hg+ (methylmercury)**.