A nitrogen atom needs to gain three electrons to attain a noble gas electron configuration. Here's why:

* Nitrogen's Electron Configuration: Nitrogen has an atomic number of 7, meaning it has 7 protons and 7 electrons. Its electron configuration is 1s² 2s² 2p³.

* Noble Gas Configuration: The nearest noble gas to nitrogen is neon (Ne), which has an electron configuration of 1s² 2s² 2p⁶.

* Gaining Electrons: To achieve the stable, full octet of electrons like neon, nitrogen needs to gain three more electrons to fill its 2p orbital.

This is why nitrogen tends to form anions with a -3 charge (N³⁻).