Nonmetal inconsistently classified by different authors. Elements sometimes also classified as nonmetals are the metalloids boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), and astatine (At). The nonmetal selenium (Se) is sometimes instead classified as a metalloid, particularly in environmental chemistry. Nonmetals show more variability in their properties than do metals. These properties are largely determined by the interatomic bonding strengths and molecular structures of the nonmetals involved, both of which are subject to variation as the number of valence electrons in each nonmetal varies. Metals, in contrast, have more homogenous structures and their properties are more
Post-transition metal which verge on the nonmetals. The peculiar metals occur towards the ends of the rows of the periodic table and include 'approximately:' gallium, indium, and thallium; carbon, silicon '(both of which have some metallic properties, though we have previously treated them as nonmetals),' germanium and tin; arsenic, antimony, and bismuth; and selenium '(which is partly metallic)' and tellurium. The ordinary metals have centro-symmetrical crystalline structures whereas the peculiar metals have structures involving directional bonding. More recently, Joshua observed that the peculiar metals have mixed metallic-covalent bonding. Farrell and Van Sicien use the term "poor metal", for simplicity, 'to denote one