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The chemical elements can be broadly divided into metals, metalloids, and nonmetals according to their shared physical and chemical properties.All elemental metals have a shiny appearance (at least when freshly polished); are good conductors of heat and electricity; form alloys with other metallic elements; and have at least one basic oxide.
It has an orthorhombic crystalline structure with a flaky habit. Iodine is semiconductor in the direction of its planes, with a band gap of about 1.3 eV and a conductivity of 1.7 × 10 −8 S•cm −1 at room temperature. This is higher than selenium but lower than boron, the least electrically conducting of the recognised metalloids.
This results in six or seven sets of nonmetals, depending on the treatment of boron, which in some cases is regarded as a metalloid. The size of the group 14 set, and the sets of nonmetal pnictogens, chalcogens, and halogens will vary depending on how silicon, germanium, arsenic, antimony, selenium, tellurium, and astatine are treated.
[n 7] The Goldhammer–Herzfeld ratio, roughly equal to the cube of the atomic radius divided by the molar volume, [56] [n 8] is a simple measure of how metallic an element is, the recognised metalloids having ratios from around 0.85 to 1.1 and averaging 1.0.
one has a metalloid-like allotrope (grey Sn, which forms below 13.2 °C [47]) all or nearly all form allotropes some (e.g. red B , yellow As ) are more nonmetallic in nature
Recognition status, as metalloids, of some elements in the p-block of the periodic table. Percentages are median appearance frequencies in the lists of metalloids. [n 2] The staircase-shaped line is a typical example of the arbitrary metal–nonmetal dividing line found on some periodic tables.
Twenty-three nonmetals. H is shown over Li and F; Germanium, As, Se, and Te are later referred to as metalloids; Sb is shown as a nonmetal but later referred to as a metal. They write, "Whilst these heavier elements [Se and Te] look metallic they show the chemical properties of non-metals and therefore come into the category of "metalloids" (p ...
[202] [203] The idea of designating elements like arsenic as metalloids had been considered. [199] By as early as 1866, some authors began preferring the term "nonmetal" over "metalloid" to describe nonmetallic elements. [204] In 1875, Kemshead [205] observed that elements were categorized into two groups: non-metals (or metalloids) and metals ...