Here's why:

* Nitrogen's small atomic size: This results in a high electron density, making it very difficult to remove electrons. This means nitrogen is highly electronegative and readily forms bonds with other atoms.

* Triple bond in N2: Nitrogen exists as a diatomic molecule (N2) with a strong triple bond between the two nitrogen atoms. This makes the N2 molecule very stable and unreactive under standard conditions. However, this stability means that when nitrogen does react, it releases a significant amount of energy.

* Other elements in the family: The reactivity of the other elements in the nitrogen family (phosphorus, arsenic, antimony, and bismuth) decreases down the group. This is because the atomic size increases, making it easier to remove electrons and reducing the electronegativity.

Therefore, while nitrogen is relatively unreactive under normal conditions due to its strong triple bond, it is the most reactive element in the nitrogen family when it does react.