According to Wikipedia, (2018) in chemistry, a nonmetal (or non-metal) is a chemical element that mostly lacks metallic attributes. Physically, nonmetals tend to have relatively low melting and boiling points, and densities, are mostly brittle if solid, and are usually poor conductors of heat and electricity; chemically, they tend to have relatively high ionization energy, electron affinity, and electronegativity values, and gain or share electrons when they react with other elements or compounds. Seventeen elements are generally classified as nonmetals; most are gases (hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon); one is a liquid (bromine), and a few are solids (carbon, phosphorus, sulfur, selenium, and iodine) (Wikipedia, 2018).
In this database we divided the „Nonmetals” group in the following subgroups according to the relative homogeneity of the halogens:
- Halogens (fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At) and their compounds;
- Other nonmetals (hydrogen (H), carbon (C), nitrogen (N), oxygen (O), phosphorus (P)*, sulphur (sulfur) (S), selenium (Se)) and their compounds;
- Noble gases (helium (He)*, neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Ra) and element 118 (Uuo).
Halogens: The halogen elements are a subset of the nonmetals. They comprise Group 17 of the periodic table, from fluorine (F) through astatine (At). They are generally very chemically reactive and are present in the environment as compounds rather than as pure elements. They were given the name halogen, from the Greek roots hal- (“salt”) and -gen (“to produce”), because they all produce sodium salts of similar properties, of which sodium chloride—table salt, or halite—is best known (Christe et al, 2017). The halogen elements show great resemblances to one another in their general chemical behaviour and in the properties of their compounds with other elements. There is, however, a progressive change in properties from fluorine through chlorine, bromine, and iodine to astatine—the difference between two successive elements being most pronounced with fluorine and chlorine (Christe et al, 2017).
Other non-metals: According to Wikipedia, (2018) H, C, N, P, O, S are sometimes referred to or categorised as organogens (Ivanenko et al, 2011), CHONPS elements (Challoner, 2014) or biogens (Crawford, 1968). Collectively these six nonmetals comprise the bulk of life on Earth (Berkowitz, 2012).
Noble gases: The inert, or noble, gases comprise Group 18. They are generally very stable chemically and exhibit similar properties of being colourless and odourless.
* on the 2017 CRMS (27) list
Christe, K., Schneider, S., Gutmann, V. (2017) Halogen element, Encyclopædia Britannica, Encyclopædia Britannica, inc. Available from: https://www.britannica.com/science/halogen-element, Accessed: 04th July, 2018
Crawford, F.H. (1968) Introduction to the science of physics, Harcourt, Brace & World, New York
Ivanenko, N.B., Ganeev AA, Solovyev ND & Moskvin LN (2011) "Determination of trace elements in biological fluids", Journal of Analytical Chemistry, vol. 66, no. 9, pp. 784–799 (784), doi:10.1134/S1061934811090036
Wikipedia (2018) Nonmetal, Available from: https://en.wikipedia.org/wiki/Nonmetal, Accessed: 04th July, 2018
CRMs (27) (2017) COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL COMMITTEE AND THE COMMITTEE OF THE REGIONS on the 2017 list of Critical Raw Materials for the EU