Final answer:
Nitrogen must gain three electrons to achieve a noble-gas electron configuration, transforming it into a nitride ion with a 3-charge.
Step-by-step explanation:
Nitrogen, with an atomic number of 7, requires extra electrons to obtain a noble-gas electron configuration. Nitrogen's position in the periodic table (group 15) indicates that it is a nonmetal, prone to forming negative ions known as anions.
To achieve the electron configuration of the noble gas neon, which is the nearest noble gas with a complete outer shell, a nitrogen atom must gain three electrons. This addition of three electrons gives nitrogen a total of ten electrons, which is the same as neon, a noble gas with an atomic number of 10. Consequently, a nitrogen atom gains three electrons to become N3-, also known as a nitride ion.