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This is an accepted version of this page This is the latest accepted revision, reviewed on 25 February 2025. This article is about the chemical element. For other uses, see Iodine (disambiguation). Chemical element with atomic number 53 (I) Iodine, 53 I Iodine Pronunciation / ˈ aɪ ə d aɪ n, - d ɪ n, - d iː n / (EYE -ə-dyne, -din, -deen) Appearance lustrous metallic gray solid ...
Most metal iodides with the metal in low oxidation states (+1 to +3) are ionic. Nonmetals tend to form covalent molecular iodides, as do metals in high oxidation states from +3 and above. Both ionic and covalent iodides are known for metals in oxidation state +3 (e.g. scandium iodide is mostly ionic, but aluminium iodide is not).
A metalloid is an element that possesses a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals, and which is therefore hard to classify as either a metal or a nonmetal. This is a generic definition that draws on metalloid attributes consistently cited in the literature.
In 1802 the term "metalloids" was introduced for elements with the physical properties of metals but the chemical properties of non-metals. [194] However, in 1811, the Swedish chemist Berzelius used the term "metalloids" [ 195 ] to describe all nonmetallic elements, noting their ability to form negatively charged ions with oxygen in aqueous ...
The nonmetals are divided into four classes that complement a four-fold division of the metals, with the noble metals treated as a subset of the transition metals. The metalloids are treated as chemically weak nonmetals, in a manner analogous to their chemically weak frontier metal counterparts.
From left to right in the periodic table, the nonmetals can be divided into the reactive nonmetals and the noble gases. The reactive nonmetals near the metalloids show some incipient metallic character, such as the metallic appearance of graphite, black phosphorus, selenium and iodine. The noble gases are almost completely inert.
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.
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. Iodine is an insulator in the direction perpendicular to its planes.