Metalloids are elements that occur in groups 13 to 17 of the periodic table. As their name suggests, metalloids possess characteristics of metals and nonmetals. Typical characteristics of metals include a shiny luster, some degree of malleability and an ability to conduct electricity or heat. Nonmetals are typically nonlustrous, brittle and poor conductors of electricity. Elements in the metalloid group may display any of these characteristics, though some elements primarily have metallic characteristics.
Boron is a nonmetal that can occur as an amorphous solid, or have the orderly crystalline structure typical of metals. It has a density of 2.37 g/cm^3, and an atomic weight of 10.811. Its isotope boron-10 is a good absorber of neutrons, which makes it useful in the control rods of nuclear reactors. Boron also imparts a green color to flares and fireworks, and is an ingredient in the borosilicate glass commonly used in laboratories.
Silicon is one of the most abundant elements on Earth, due to its presence in silicates, which that make up much of Earth's crust. At room temperature, it can be both crystalline and amorphous. The amorphous, nonmetallic form is a brown powder, while the crystalline form has a metallic luster. Silicon has an atomic weight of 28.0855 and a density of 2.3296 g/cm^3. It is widely used in brick, concrete and pottery.
A gray-white and brittle metalloid, germanium is common in the semiconductor industry as a transistor, which gives it the characteristics of a metal. It has an atomic weight of 72.64 and a density of 5.323 g/cm^3. It's a phosphor in fluorescent lamps and when combined to form a compound can be used in optical glasses. Because it’s transparent to infrared radiation, it’s useful in infrared detecting optics.
Arsenic has many characteristics of a metal. It comes in gray, black, yellow and gray crystalline forms, and is solid at room temperatures. It has an atomic weight of 74.92160 and a density of 5.776 g/cm^3. It's a potent poison that's in rat poisons, weed killers, doping agents and insecticides. Arsenic's boiling point is lower than its melting point, which means that it changes directly from a solid to a gas at standard atmospheric pressures.
A largely metallic element, antimony most often occurs as a lustrous, hard crystal, but other forms display the brittleness characteristic of nonmetals. It has a density of 6.685 g/cm^3, and an atomic weight of 121.760. It’s useful in the manufacture of car batteries, paints and glass.
Tellurium is a brittle, metallic element that is a solid at room temperature. It’s typically doped with medals like gold, silver and tin. It has an atomic weight of 127.60 and a density of 6.232 g/cm^3. It's used commercially in refining copper, and as an alloy in lead and stainless steel. Tellurium is also a colorant for ceramics.
The radioactive metalloid polonium is a strong emitter of alpha particles that form an isotope of lead. It has the characteristics of a hard, dense metal with an atomic weight of 127.60 and a density of 9.32 g/cm^3. It's often used to eliminate static electricity in machinery.
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- Periodic Table: The Element Germanium
- Periodic Table: The Element Arsenic
- Jefferson Lab: Antimony
- Jefferson Lab: Tellurium
- Periodic Table: The Element Antimony
- Periodic Table: The Element Tellurium
- Periodic Table: The Element Polonium
- Jefferson Lab: Boron
- Jefferson Lab: Silicon
- Jefferson Lab: Germanium
- Jefferson Lab: Arsenic
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