Chemical elements semimetals

Astatine is located just below iodine, which suggests that it should have some of the same chemical properties as iodine, even though it also acts more hke a metal or semimetal than does iodine. It is a fairly heavy element with an odd atomic number, which assisted chemists in learning more about this extremely rare element. The 41 isotopes are man-made in atomic reactors, and most exist for fractions of a second. The elements melting point is about 302°C, its boiling point is approximately 337°C, and its density is about 7g/cm. ... 

Silicon (Si) is the second most abundant element in the earth s crust, contributing around 28%. Silicon acts as a nonmetal in its chemical behavior but its electrical and physical properties are those of a semimetal. Crystalline silicon is a gray, lustrous solid. The chemistry of silicon is dominated by compounds that contain the silicon-oxygen (Si-O) linkage. 

Examine the elements in green boxes bordering the stair-step line in Figure 6-7. These elements are called metalloids, or semimetals. Metalloids are elements with physical and chemical properties of both metals and non-metals. Silicon and germanium are two of the most important metalloids, as they are used extensively in computer chips and solar cells. Applications that make use of the properties of nonmetals, transition metals, and metalloids are shown in Figure 6-8. Do the CHEMLAB at the end of this chapter to observe trends among various elements. 

The elements have been classified empirically based on similarities in their physical or chemical properties. Metals and nonmetals are distinguished by the presence (or absence) of a characteristic metallic luster, good (or poor) ability to conduct electricity and heat, and malleability (or brittleness). Certain elements (boron, silicon, germanium, arsenic, antimony, and tellurium) resemble metals in some respects and nonmetals in others, and are therefore called semimetals or metalloids. Their ability to conduct electricity, for example, is much worse than metals, but is not essentially zero like the nonmetals. 

Antimony is a metalloid element, or a semimetal, its chemical behavior being between those of metals and nonmetals. It is a substance that was known in the ancient world. Antimony sulfide was used as cosmetic eye paint in ancient Egypt, and artifacts composed of almost pure antimony have been found at archaeological sites. Pure antimony is silvery gray and metallic-looking. If antimony is melted and then allowed to crystallize, it manifests a characteristic pattern known as the star of antimony. 

The heavy black line in Fig. 20.1 separates the metals from the nonmetals, except for one case. Flydrogen, which appears on the metal side, is a nonmetal. Some elementsjust on either side of this line, such as silicon and germanium, exhibit both metallic and non-metallic properties. These elements are often called metalloids, or semimetals. The fundamental chemical difference between metals and nonmetals is that metals tend to lose their valence electrons to form cations, which usually have the valence electron configuration of the noble gas from the preceding period. On the other hand, nonmetals tend to gain electrons to form anions that exhibit the electron configuration of the noble gas in... 

Metalloid is a term for elements that are sort-of metals, and sort-of not metals. Sometimes this group of elements is referred to as semimetals. To be more precise, these elements exhibit some of the physical and chemical properties of metals. Generally metalloids have some electrical conductivity, but not nearly as much as true metals. Because of these ambiguous definitions, even which elements are called metalloids can vary. Usually boron, silicon, germanium, arsenic, antimony, and tellurium are included as metalloids sometimes polonium and astatine rarely selenium. 

Simply stated, inorganic chemistry deals with the 117 elements in the periodic table other than carbon. The elements in the periodic table are broadly grouped into three classifications metals, nonmetals, and metalloids (or semimetals). Inorganic chemists describe the physical and chemical properties of the elements themselves, as well as all of the chemical compounds the elements can form, both in nature and in the laboratory. 

One example is the ability of solids to conduct electricity, which is measured by their electrical resistivity. Some typical single-element metallic solids (such as Ag, Cu, Al), have room-temperature resistivities of l-5pf2-cm, while some metallic alloys (like nichrome) have resistivities of lO p cm. All these solids are considered good conductors of electrical current. Certain single-element solids (like C, Si, Ge) have room-temperature resistivities ranging from 3.5 x lO pS -cm (for graphitic C) to 2.3 x lO V -cm (for Si), and they are considered semimetals or semiconductors. Finally, certain common solids like wood (with a rather complex structure and chemical composition) or quartz (with a rather simple structure and composed of two elements. Si and O), have room-temperature resistivities of lO -lO pS -cm (for wood) to lO p cm (for quartz). These solids are... 

Silicon, the second most abundant element in the earth s cmst, is a semimetal found widely distributed in silica and silicates (see Section 10.5). Approximately 85% of the earth s crust is composed of these substances. Although silicon is found in some steel and aluminum alloys, its major use is in semiconductors for electronic devices (see the Chemical Impact in Section 10.5). 

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