Which of the following species does / do not exist ?

Options

A. `OF_(4)`
B. `NH_(2)^(-)`
C. `NCl_(5)`
D. `IC l_(3)^(2-)`

Answer

To determine which of the given species do not exist, we will analyze each species based on the rules of chemical bonding, particularly focusing on the octet rule and the availability of d orbitals for expansion of valency.

### Step-by-Step Solution:

1. **Analyze OF4 (Oxygen Tetrafluoride)**:
- Oxygen typically forms two bonds to complete its octet.
- In OF4, oxygen would need to form four sigma bonds with fluorine.
- Oxygen does not have d orbitals to accommodate more than two bonds.
- **Conclusion**: OF4 does not exist.

2. **Analyze NH2- (Amide Ion)**:
- Nitrogen has five valence electrons and needs three more to complete its octet.
- In NH2-, nitrogen forms two bonds with hydrogen and has one extra electron (due to the negative charge).
- This configuration allows nitrogen to effectively complete its octet.
- **Conclusion**: NH2- exists.

3. **Analyze NCl5 (Nitrogen Pentachloride)**:
- Nitrogen typically forms three bonds to complete its octet.
- To form NCl5, nitrogen would need to form five bonds.
- Nitrogen lacks d orbitals to expand its valency beyond four bonds.
- **Conclusion**: NCl5 does not exist.

4. **Analyze ICl3 2- (Iodine Trichloride Ion)**:
- Iodine can expand its octet due to the presence of d orbitals.
- However, the presence of a 2- charge on ICl3 is questionable since it would imply an unusual electron configuration.
- Iodine typically forms three bonds with chlorine, and having a 2- charge is not stable for this configuration.
- **Conclusion**: ICl3 2- does not exist.

### Final Conclusion:
The species that do not exist are:
- OF4
- NCl5
- ICl3 2-

### Summary of Results:
- **Species that do not exist**: OF4, NCl5, ICl3 2-
- **Species that exists**: NH2-