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

Explanation

To answer the question regarding why the cyanide ion (CN⁻) is chemically reactive while nitrogen gas (N₂) is chemically inert, despite both being isoelectronic, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Isoelectronic Species**:
- Isoelectronic species are atoms, ions, or molecules that have the same number of electrons. In this case, both CN⁻ and N₂ have a total of 10 electrons.

2. **Molecular Structure**:
- CN⁻ has a linear structure with a triple bond between carbon and nitrogen (C≡N) and an additional lone pair on the carbon atom. This gives it a polar character due to the difference in electronegativity between carbon and nitrogen.
- N₂ also has a linear structure with a triple bond (N≡N), but it is symmetrical, resulting in a non-polar molecule.

3. **Polarity and Chemical Reactivity**:
- The polarity of CN⁻ means it has a dipole moment, making it a strong nucleophile. This allows CN⁻ to readily donate its electron pair to electrophiles, leading to chemical reactions.
- In contrast, N₂ being non-polar has a dipole moment of zero, which contributes to its chemical inertness. The symmetrical distribution of charge means it does not readily participate in chemical reactions.

4. **Bond Energy Considerations**:
- The bond energy of the N≡N bond in nitrogen gas is very high, making it stable and less reactive under normal conditions. The strong bond energy contributes to the inertness of N₂.
- In comparison, the CN⁻ ion is less stable and more reactive due to its ability to participate in chemical reactions.

5. **Conclusion**:
- Therefore, the key reason CN⁻ is chemically reactive while N₂ is inert is due to the polarity of CN⁻, which allows it to act as a nucleophile, contrasted with the non-polar nature of N₂, which leads to its inertness.