When nitrogen fills its valence shell, it typically gains three electrons. Nitrogen has five valence electrons (with a configuration of 1s² 2s² 2p³), and to achieve a full octet (which consists of eight electrons in the valence shell), it needs to gain three additional electrons.
Thus, the correct response is:
Three electrons are gained, creating N−3.
This can also be represented as:
Three electrons are gained, creating uppercase N superscript negative 3 end superscript .