Depending on the metallic element, the nitrides may designated as ionic, covalent, or interstitial, as
is the case with hydrides, carbides, and borides. Boron nitrides are known that have the diamond or
graphite structure (these materials were discussed in Chapter 13). Binary compounds containing nitrogen
and most other elements are known, but because N 2 is not very reactive, most are not prepared by
combination of the elements. If the difference between the electronegativity of nitrogen and that of
the other element is about 1.6 or greater, the compounds will be essentially ionic in nature, and they
can be prepared by direct combination of the elements as shown earlier.