Why does nitrogen show poor tendency towards catenation?

The N – N single bond is weaker and unstable

The correct answer is option 4. The N – N single bond is weaker and unstable.

Nitrogen shows a poor tendency towards catenation, which is the ability to form chains of like atoms, primarily because the N – N single bond is weaker and unstable.

Bond Strength and Stability: The \(N–N\) single bond is relatively weak compared to the single bonds of other group 15 elements and carbon. The bond dissociation energy of the \(N–N\) single bond is significantly lower, meaning it requires less energy to break this bond. This weakness leads to instability in \(N–N\) single bonds. The bond dissociation energy for the \(N–N\) bond is about 163 kJ/mol, which is much lower compared to the \(C–C\) bond in carbon (about 346 kJ/mol). This weakness arises because of the lone pairs on each nitrogen atom that repel each other when they are bonded together, making the bond less stable.

Multiple Bond Formation: Nitrogen atoms tend to form multiple pπ–pπ bonds (as seen in \(N≡N\) in \(N_2\)) rather than forming single bonds. This preference for multiple bonding over single bonding further reduces the tendency for nitrogen to form long chains through single bonds (catenation). The triple bond in nitrogen \((N≡N)\) is very strong, with a bond dissociation energy of about 946 kJ/mol. This strong bond makes the molecular nitrogen \((N_2)\) very stable and relatively inert at room temperature, reducing the tendency to form reactive single bonds.

Electronic Configuration:

Nitrogen’s electronic configuration (1s² 2s² 2p³) allows it to form three covalent bonds, achieving a stable octet. However, forming \(N–N\) single bonds would involve higher energy configurations due to lone pair-lone pair repulsion.

While options about multiple bonds and octet completion contribute to understanding nitrogen's chemistry, the most direct reason for its poor catenation tendency is the weak and unstable nature of the N–N single bond. Therefore, the correct answer is: 4. The N – N single bond is weaker and unstable