Nonmetals rarely lose electrons in chemical reactions because their ionization
energies are too high. However, a nonmetal atom can acquire enough electrons to
complete its valence shell and form an anion with an octet corresponding to the
configuration of the next noble gas (1s2 in the case of the hydride ion, H), FIG. 3.3.
It does not gain more electrons, because any additional electrons would have to be
accommodated in a higher-energy shell. To form a monatomic anion, we add
enough electrons to complete the valence shell. For example, nitrogen has five
valence electrons (1); so three more electrons are needed to reach a noble-gas configuration,
that of neon. Therefore, the nitride ion will be N3 (2). Notice that in
each case the ion has the electron configuration of the next noble gas.