Metalloid what classification criteria are used. Emsley recognised four metalloids (germanium, arsenic, antimony, and tellurium); James et al. listed twelve (Emsley's plus boron, carbon, silicon, selenium, bismuth, polonium, moscovium, and livermorium). On average, seven elements are included in such lists; individual classification arrangements tend to share common ground and vary in the ill-defined margins. A single quantitative criterion such as electronegativity is commonly used, metalloids having electronegativity values from 1.8 or 1.9 to 2.2. Further examples include packing efficiency (the fraction of volume in a crystal structure occupied by atoms) and the Goldhammer-Herzfeld criterion ratio. The commonly recognised metalloids have packing
Antimony risk index. This indicates that it has currently the second highest supply risk for chemical elements or element groups which are of economic value to the British economy and lifestyle. Furthermore, antimony was identified as one of 20 critical raw materials for the EU in a report published in 2014 (which revised the initial report published in 2011). As seen in Figure xxx antimony maintains high supply risk relative to its economic importance. 92% of the antimony is imported from China, which is a significantly high concentration of production. Much analysis has been conducted in the U.S. toward defining which