They also said that metalloids are typically semiconductors, though antimony and arsenic (semimetals from a physics perspective) have electrical conductivities approaching those of metals.
Selenium and polonium are suspected as not in this scheme, while astatine's status is uncertain.
Rayner-Canham has argued that these similarities extend to carbon-phosphorus, nitrogen-sulfur, and into three d-block series.Five elements are less frequently so classified: carbon, aluminium, selenium, polonium, and astatine.On a standard periodic table, all eleven are in a diagonal area in the p-block extending from boron at the upper left to astatine at lower right, along the dividing line between metals and nonmetals shown on some periodic tables. Most of their other physical and chemical properties are intermediate in nature.Typical metalloids have a metallic appearance, but they are brittle and only fair conductors of electricity. Metalloids are usually too brittle to have any structural uses.They and their compounds are used in alloys, biological agents, catalysts, flame retardants, glasses, optical storage and optoelectronics, pyrotechnics, semiconductors, and electronics.The additional pull on outer electrons as nuclear charge increases generally outweighs the screening effect of having more electrons.