These properties may prove very useful in a wide range of applications, such as vastly improved computer chips and circuits, better batteries and solar cells, and stronger and lighter structural materials. Figure 8. Graphene sheets can be formed into buckyballs, nanotubes, and stacked layers.
In a crystalline solid, the atoms, ions, or molecules are arranged in a definite repeating pattern, but occasional defects may occur in the pattern. Several types of defects are known, as illustrated in Figure 9.
Vacancies are defects that occur when positions that should contain atoms or ions are vacant. Less commonly, some atoms or ions in a crystal may occupy positions, called interstitial sites , located between the regular positions for atoms.
Other distortions are found in impure crystals, as, for example, when the cations, anions, or molecules of the impurity are too large to fit into the regular positions without distorting the structure. Trace amounts of impurities are sometimes added to a crystal a process known as doping in order to create defects in the structure that yield desirable changes in its properties. For example, silicon crystals are doped with varying amounts of different elements to yield suitable electrical properties for their use in the manufacture of semiconductors and computer chips.
Figure 9. Types of crystal defects include vacancies, interstitial atoms, and substitutions impurities. Some substances form crystalline solids consisting of particles in a very organized structure; others form amorphous noncrystalline solids with an internal structure that is not ordered.
The main types of crystalline solids are ionic solids, metallic solids, covalent network solids, and molecular solids. The properties of the different kinds of crystalline solids are due to the types of particles of which they consist, the arrangements of the particles, and the strengths of the attractions between them. Because their particles experience identical attractions, crystalline solids have distinct melting temperatures; the particles in amorphous solids experience a range of interactions, so they soften gradually and melt over a range of temperatures.
Some crystalline solids have defects in the definite repeating pattern of their particles. These defects which include vacancies, atoms or ions not in the regular positions, and impurities change physical properties such as electrical conductivity, which is exploited in the silicon crystals used to manufacture computer chips. Ice has a crystalline structure stabilized by hydrogen bonding. These intermolecular forces are of comparable strength and thus require the same amount of energy to overcome.
As a result, ice melts at a single temperature and not over a range of temperatures. The various, very large molecules that compose butter experience varied van der Waals attractions of various strengths that are overcome at various temperatures, and so the melting process occurs over a wide temperature range. Skip to main content. Module Liquids and Solids. Search for:. The Solid State of Matter Learning Objectives By the end of this section, you will be able to: Define and describe the bonding and properties of ionic and molecular metallic and covalent network crystalline solids Describe the main types of crystalline solids: ionic solids, metallic solids, covalent network solids, and molecular solids Explain the ways in which crystal defects can occur in a solid.
Figure 3. Sodium chloride is an ionic solid. Figure 4. Copper is a metallic solid. Graphene: Material of the Future Carbon is an essential element in our world. Key Concepts and Summary Some substances form crystalline solids consisting of particles in a very organized structure; others form amorphous noncrystalline solids with an internal structure that is not ordered.
Exercises What types of liquids typically form amorphous solids? At very low temperatures oxygen, O 2 , freezes and forms a crystalline solid. It is also relatively easy for metals to lose these valence electrons, which explains why metallic elements usually form cations when they make compounds.
The foods and beverages we eat and drink all have different phases: solid, liquid, and gas. How do we ingest gases? Carbonated beverages have gas, which sometimes cause a person to belch. However, among the solids we eat, three in particular are, or are produced from, rocks. Yes, rocks! The first one is NaCl, or common salt. Salt is the only solid that we ingest that is actually mined as a rock hence the term rock salt ; it really is a rock.
Salt preserves food, a function that was much more important before the days of modern food preparation and storage. The fact that saltiness is one of the major tastes the tongue can detect suggests a strong evolutionary link between ingesting salt and survival.
There is some concern today that there is too much salt in the diet; it is estimated that the average person consumes at least three times as much salt daily than is necessary for proper bodily function. However, we do not mine these substances directly from the ground; we mine trona, whose chemical formula is Na 3 H CO 3 2.
Another process, called the Solvay process, is also used to make Na 2 CO 3. Either way, we get these two products from the ground i. NaHCO 3 is also known as baking soda, which is used in many baked goods. Na 2 CO 3 is used in foods to regulate the acid balance. It is also used in laundry where it is called washing soda to interact with other ions in water that tend to reduce detergent efficiency.
Skip to content Chapter Solids and Liquids. Describe the general properties of a solid. Describe the six different types of solids. Predict the type of crystal exhibited by each solid. Silver is a metal, so it would exist as a metallic solid in the solid state.
CO 2 is a covalently bonded molecular compound. In the solid state, it would form molecular crystals. You can actually see the crystals in dry ice with the naked eye.
Test Yourself Predict the type of crystal exhibited by each solid. I 2 Ca NO 3 2 Answers molecular crystals ionic crystals. Solids can be divided into amorphous solids and crystalline solids. Crystalline solids can be ionic, molecular, covalent network, or metallic. Questions What is the difference between a crystalline solid and an amorphous solid? The difference between metals, insulators, and semiconductors is the size of the band gap.
Metals have no band gap. In other words, the conduction band and valence band overlap, so an atom is not bound to any particular atom. If it has enough energy to leave, it just leaves. Semiconductors have a small band gap. If there is enough energy to pass this barrier, the material conducts. Insulators have a large band gap. These terms are practical—anything which is considered an insulator has a band gap that is too large to cross in a realistic scenario. Trying to pass too much current through many insulators will destroy the material before electrons have enough energy to jump across the band gap.
Conductivity measures the amount of electrical current a material can carry. This equation was generalized for any situation involving electrical conductivity including ion conduction , but in most cases the charge carrier is just electrons. So conductivity is basically just how many electrons can squeeze through the wire in a given amount of time. Usually, if engineers can change the conductivity of something, they are changing , the mobility of electrons.
For example, grain boundaries can scatter electrons, reducing the speed they travel through the wire. Precipitates and alloying elements reduce conductivity for the same reason. The opposite of conductivity is resistivity or resistance. Resistivity is the intrinsic version of resistance. As in metals, increasing temperature decreases. But in semiconductors, higher thermal energy means more electrons can pass from the valence band to the conduction band.
So while mu decreases slightly, n increases a lot! In fact, mobility is so important to resistance that at absolute zero, when lattice vibrations cease and electrons can pass through a metal unimpeded, metals can become superconductors. Shape is probably what you learned in high school, regarding conductivity.
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