The cyanide ion `CN and N_(2)` are isoelectronic, but in contrast to `CN^(-), N_(2)` is chemically inert, because of

Options

A. low bond energy
B. absence of bond polairty
C. unsymmetical electron distribution
D. Presence of more number of electron is bonding orbitals.

Explanation

To solve the question regarding why the cyanide ion (CN⁻) is chemically reactive while nitrogen gas (N₂) is chemically inert, even though they are isoelectronic, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Isoelectronic Species**:
- Both CN⁻ and N₂ have the same number of electrons. CN⁻ has 14 electrons (6 from carbon and 7 from nitrogen, plus 1 extra due to the negative charge), and N₂ also has 14 electrons (7 from each nitrogen atom).

2. **Identifying the Nature of the Molecules**:
- CN⁻ is a heteroatomic ion consisting of carbon and nitrogen, while N₂ is a homoatomic molecule made up of two nitrogen atoms.

3. **Bonding Characteristics**:
- In CN⁻, the presence of a negative charge leads to a polar bond due to the difference in electronegativity between carbon and nitrogen. This polar nature contributes to its reactivity.
- In contrast, N₂ has a triple bond between two nitrogen atoms, which is non-polar because both atoms are the same. This lack of polarity contributes to its stability and inertness.

4. **Bond Energy Considerations**:
- The bond in N₂ is very strong (triple bond), which contributes to its inertness. High bond energy means that it requires a significant amount of energy to break the bond, making it less reactive.
- CN⁻, on the other hand, has a polar bond that can participate in chemical reactions more readily.

5. **Conclusion**:
- The key reason for the chemical inertness of N₂ compared to the reactivity of CN⁻ is the **absence of bond polarity** in N₂, which makes it stable and less likely to react with other substances.

### Final Answer:
The correct option is **B: Absence of bond polarity**.