Nonmetal

Non-metals, (formerly called metalloids ) are chemical elements, where the typical metallic properties such as good electrical and thermal conductivity, luster, hardness, and good formability missing.

Non-metals according to the above definition are: carbon, nitrogen, oxygen, phosphorus, sulfur, selenium, halogens (fluorine, chlorine, bromine, iodine, and astatine ), and the noble gases (helium, neon, argon, krypton, xenon, radon). Furthermore, hydrogen is counted as non-metals, since it does not have the above properties as well.

The limits to semiconductors and metals are fluid, which is on the one hand by the different views of the subject areas (chemistry and physics ) due to the other fact that modifications of an element can have completely different properties, and so similar to the partial properties of can have of metals. The best known modifications of carbon, graphite and diamond, are a good example. Thus, in contrast to graphite diamond on a very good electrical conductivity. The diamond on the other hand, despite its very poor electrical conductivity of a very high thermal conductivity (better than metals). The reason for this lies in the different mechanisms of heat transfer in diamond and metals.

However, this is only the case for a portion of the non-metals. The metallic modifications may form in some cases only under extreme conditions, for example, hydrogen or iodine at high pressure.

The electron affinity of non-metals (with the exception of the noble gases ), is generally the highest of the chemical elements. This means that non-bonded atoms are eager to take up electrons to obtain a stable fully occupied valence shell (see octet rule ), rather than leave like most metals electrons. Exceptions is here with the aforementioned noble gases, especially nitrogen.