Which of the following exists as dimer?

Options

A. `N_(2)O_(5)`
B. `N_(2)O`
C. `P_(2)O_(3)`
D. `Bi_(2)O_(3)`

Answer

To determine which of the given compounds exists as a dimer, we will analyze each option step by step.

### Step 1: Analyze N2O5
- **Structure**: N2O5 is composed of two nitrogen atoms and five oxygen atoms. Its structure can be represented as N-O-N with double bonds to oxygen.
- **Dimerization**: N2O5 does not exist as a dimer; it is a stable molecular compound on its own.

### Step 2: Analyze N2O
- **Structure**: N2O, known as nitrous oxide or laughing gas, consists of two nitrogen atoms and one oxygen atom.
- **Dimerization**: N2O does not exist as a dimer either; it is a simple molecular compound.

### Step 3: Analyze P2O3
- **Structure**: P2O3 consists of two phosphorus atoms and three oxygen atoms. It can be represented in a way that suggests it might form a dimer.
- **Dimerization**: However, P2O3 is not a dimer in its stable form. It can be confused with P4O6, which is a molecular form that contains multiple P2O3 units but is not a dimer itself.

### Step 4: Analyze Bi2O3
- **Structure**: Bi2O3 consists of two bismuth atoms and three oxygen atoms.
- **Dimerization**: Bi2O3 does not exist as a dimer; it is a stable compound on its own.

### Conclusion
After analyzing all the options, we find that none of the compounds listed (N2O5, N2O, P2O3, Bi2O3) exist as dimers. However, P2O3 can be confused with P4O6, which is a polymeric form. Therefore, the answer to the question is that none of the given options exist as dimers in their stable forms.

### Final Answer
None of the options exist as dimers.