Elements of group - 15 compounds in +5 oxidation state. However, bismuth forms only one well characterised compound in +5 oxidation state. The compound is

Options

A. `Bi_(2)O_(5)`
B. `BiF_(5)`
C. `BiCl_(5)`
D. `Bi_(2)S_(5)`

Explanation

To determine the well-characterized compound of bismuth in the +5 oxidation state among the given options, we can follow these steps:

### Step 1: Understand the oxidation states of bismuth
Bismuth (Bi) can exhibit multiple oxidation states, primarily +3 and +5. However, the stability of the +5 oxidation state decreases as we move down the group in the periodic table due to the inert pair effect.

**Hint:** Recall that the inert pair effect refers to the reluctance of the s-electrons to participate in bonding as we move down a group in the periodic table.

### Step 2: Identify the inert pair effect
The inert pair effect explains why heavier p-block elements, like bismuth, tend to favor lower oxidation states. In bismuth, the +3 oxidation state is more stable than the +5 oxidation state because the valence s electrons are less likely to participate in bonding.

**Hint:** Consider how the inert pair effect influences the oxidation states of elements in group 15.

### Step 3: Analyze the given compounds
We have four options: Bi2O5, BiF5, BiO5, and Bi2S5. We need to identify which of these compounds can exist in the +5 oxidation state.

1. **Bi2O5**: This compound can exist, but it is not well characterized as a +5 oxidation state compound.
2. **BiF5**: This compound is known to exist and is characterized by bismuth in the +5 oxidation state.
3. **BiO5**: This compound is not well characterized and does not typically exist.
4. **Bi2S5**: This compound does not involve bismuth in the +5 oxidation state.

**Hint:** Focus on the electronegativity of the elements in the compounds to determine which can stabilize the +5 oxidation state of bismuth.

### Step 4: Determine the most stable compound in +5 oxidation state
Among the options, BiF5 is the only well-characterized compound where bismuth is in the +5 oxidation state. The presence of fluorine, which is highly electronegative and small in size, allows bismuth to achieve this higher oxidation state.

**Hint:** Remember that highly electronegative elements can stabilize higher oxidation states of less electronegative elements.

### Conclusion
The well-characterized compound of bismuth in the +5 oxidation state is **BiF5**.

**Final Answer:** BiF5