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 following species does not exist, we will analyze each species based on the valence electron configuration and the ability of the central atom to accommodate the surrounding atoms.

### Step-by-Step Solution:

1. **Analyze OF4 (Oxygen Tetrafluoride)**:
- Oxygen (O) is the central atom and belongs to Group 16, having 6 valence electrons.
- The maximum number of bonds oxygen can form is typically 2 (due to its valency of -2).
- In OF4, oxygen is expected to form 4 bonds, which exceeds its bonding capacity.
- **Conclusion**: OF4 does not exist.

2. **Analyze NH2- (Amide Ion)**:
- Nitrogen (N) is the central atom and belongs to Group 15, having 5 valence electrons.
- The NH2- ion has a negative charge, indicating it has gained an extra electron, giving nitrogen a total of 6 electrons.
- Nitrogen can accommodate 3 bonds (as it can share 3 of its electrons).
- **Conclusion**: NH2- can exist.

3. **Analyze NCl5 (Nitrogen Pentachloride)**:
- Nitrogen (N) is again the central atom, with 5 valence electrons.
- NCl5 would require nitrogen to form 5 bonds with chlorine, which exceeds nitrogen's bonding capacity (it can only form 3 bonds).
- **Conclusion**: NCl5 does not exist.

4. **Analyze ICl3- (Iodine Trichloride Ion)**:
- Iodine (I) is the central atom and belongs to Group 17, having 7 valence electrons.
- The ICl3- ion has a negative charge, indicating it has gained an extra electron, giving iodine a total of 8 electrons.
- Iodine can expand its octet and accommodate more than 8 electrons due to the presence of d-orbitals.
- **Conclusion**: ICl3- can exist.

### Final Summary:
- The species that do not exist are **OF4** and **NCl5**.
- The species that can exist are **NH2-** and **ICl3-**.