Search results
Results From The WOW.Com Content Network
Boron is a semiconductor; [244] its room temperature electrical conductivity is 1.5 × 10 −6 S•cm −1 [245] (about 200 times less than that of tap water) [246] and it has a band gap of about 1.56 eV. [247] [n 23] Mendeleev commented that, "Boron appears in a free state in several forms which are intermediate between the metals and the ...
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.
Chain-melted state: Metals, such as potassium, at high temperature and pressure, present properties of both a solid and liquid. Wigner crystal : a crystalline phase of low-density electrons. Hexatic state , a state of matter that is between the solid and the isotropic liquid phases in two dimensional systems of particles.
Although compounds in the +1 (mostly ionic) oxidation state are the more numerous, thallium has an appreciable chemistry in the +3 (largely covalent) oxidation state, as seen in its chalcogenides and trihalides. [116] It and aluminium are the only Group 13 elements to react with air at room temperature, slowly forming the amphoteric oxide Tl 2 O 3.
Arsenic pentafluoride (AsF 5) is the only important pentahalide, reflecting the lower stability of the +5 oxidation state; even so, it is a very strong fluorinating and oxidizing agent. (The pentachloride is stable only below −50 °C, at which temperature it decomposes to the trichloride, releasing chlorine gas. [23])
Antimony is stable in air at room temperature but, if heated, it reacts with oxygen to produce antimony trioxide, Sb 2 O 3. [12] Antimony is a silvery, lustrous gray metalloid with a Mohs scale hardness of 3, which is too soft to mark hard objects.
At standard temperature and pressure, silicon is a shiny semiconductor with a bluish-grey metallic lustre; as typical for semiconductors, its resistivity drops as temperature rises. This arises because silicon has a small energy gap ( band gap ) between its highest occupied energy levels (the valence band) and the lowest unoccupied ones (the ...