The oxidation state of -3 is least stable in

Options

A. `As`
B. `P`
C. `Bi`
D. `Sb`

Explanation

To determine which element has the least stable oxidation state of -3 among arsenic, phosphorus, bismuth, and antimony, we can follow these steps:

### Step 1: Understand the oxidation states of group 15 elements
Group 15 elements include nitrogen, phosphorus, arsenic, antimony, and bismuth. They can exhibit various oxidation states, including negative states like -3.

### Step 2: Analyze the elements in question
- **Phosphorus (P)**: Commonly exhibits a -3 oxidation state, especially in compounds like phosphides.
- **Arsenic (As)**: Also shows a -3 oxidation state, though it is less stable than in phosphorus.
- **Antimony (Sb)**: Can exhibit a -3 oxidation state, but it is less common and less stable compared to phosphorus and arsenic.
- **Bismuth (Bi)**: Primarily exhibits positive oxidation states (+3 and +5) and is a metal. The -3 oxidation state is not stable for bismuth.

### Step 3: Determine the stability of the -3 oxidation state
- Non-metals like phosphorus and arsenic can stabilize the -3 oxidation state due to their electronegativity.
- Antimony, being a metalloid, can also exhibit a -3 state, but it is less stable than in phosphorus and arsenic.
- Bismuth, being a heavier metal, has a more metallic character and less electronegativity, making the -3 oxidation state highly unstable.

### Step 4: Conclusion
Among the elements listed, bismuth (Bi) has the least stable -3 oxidation state due to its metallic nature and tendency to prefer positive oxidation states.

### Final Answer
The oxidation state of -3 is least stable in **bismuth (Bi)**.

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