Why does molecular nitrogen contain a triple bond?

Molecular nitrogen ($N_2$) contains a triple bond because each nitrogen atom has three half-filled outer $p$ orbitals, which allow the atoms to share three pairs of electrons to achieve a stable configuration.12

In this covalent linkage, the triple bond consists of one sigma bond and two pi bonds. According to molecular orbital theory, the ten valence electrons of the $N_2$ molecule occupy the lowest-energy orbitals, resulting in a configuration that matches the :N≡N: Lewis structure.34

This triple bond is exceptionally strong, with a bond energy of 226 kilocalories per mole. Because of this high stability, molecular nitrogen is relatively inert under ordinary conditions. The tendency to form multiple bonds is particularly pronounced in nitrogen because its small atomic size and high electronegativity favor the overlap of orbitals to form pi bonds, a characteristic that distinguishes it from the heavier elements in the nitrogen group.15