When nitrogen is combined, the result is nitride, which has a formal oxidation state of -3. Nitrides are a vast class of substances with a diverse variety of characteristics and uses. Since the nitride ion, N3, is so basic that it would be protonated right away, it is never found in protic solutions. Its calculated ionic radius is 140 pm. Due to their high lattice energy, which represents the strong attraction of "N3" for the metal cation, nitrides are frequently refractory materials, much like carbides. As a result, silicon nitride, cubic boron nitride, and titanium nitride are employed as hard coatings and cutting tools. A suitable high-temperature lubricant analogous to molybdenum disulfide is hexagonal boron nitride, which assumes a layered structure. Large band gaps are common in nitride compounds. Nitride compounds frequently have wide band gaps, making them insulators or wide-bandgap semiconductors; examples include silicon nitride and boron nitride. Gallium nitride, a material with a wide band gap, is highly valued for emitting blue light in LEDs. For its invention in 2014, researchers were awarded the Nobel Prize in Physics.