To break them, the very strong ionic attractions need to be broken a displacement of only about 1 × 10 −10 m will move ions next to ions of the same charge, which results in repulsion. Hence most ionic solids have relatively high melting points for example, the melting point of NaCl is 801☌. The ions are held together by the attraction of opposite charges - a very strong force. The Na + ions and Cl − ions alternate in three dimensions, repeating a pattern that goes on throughout the sample. NaCl is an example of an ionic solid (see Figure 10.13 “An Ionic Solid”). However, there are several different types of crystalline solids, depending on the identity of the units that compose the crystal.Īn ionic solid is a crystalline solid composed of ions (even if the ions are polyatomic). There is only one type of amorphous solid. A crystal of NaCl (see Figure 10.12 “Properties of Solids”) is one example: at the atomic level, NaCl is composed of a regular three-dimensional array of Na + ions and Cl − ions. A crystalline solid is a solid that has a regular, repeating three-dimensional structure. Examples include glass and many plastics, both of which are composed of long chains of molecules with no order from one molecule to the next. An amorphous solid is a solid with no long-term structure or repetition. Here we will review the different types of solids and the bonding that gives them their properties.įirst, we must distinguish between two general types of solids. Solids can have a wide variety of physical properties because there are different types of solids. These two substances illustrate the range of properties that solids can have. (b) NaCl is transparent, hard, and colourless and does not conduct electricity or heat well in the solid state. Figure 10.12 “Properties of Solids.” (a) Sodium metal is silvery, soft, and opaque and conducts electricity and heat well. Figure 10.12 “Properties of Solids” shows two solids that exemplify the similar and dissimilar properties of solids. Many solids are opaque, but some are transparent. Solid metals conduct electricity and heat, while ionic solids do not. Appearances differ as well: most metals are shiny and silvery, but sulfur (a nonmetal) is yellow, and ionic compounds can take on a rainbow of colours. Some metals, such as sodium and potassium, are rather soft, while others, such as diamond, are very hard and can easily scratch other substances. For example, many metals can be beaten into thin sheets or drawn into wires, while compounds such as NaCl will shatter if they are struck. Solids may also demonstrate a variety of properties. They cannot be easily compressed like gases can, and they have relatively high densities. They do not fill their entire containers like gases do, and they do not adopt the shape of their containers like liquids do. The solid phase has several characteristics. At low enough temperatures, all substances are solids (helium is the lone exception), but the temperature at which the solid state becomes the stable phase varies widely among substances, from 20 K (−253☌) for hydrogen to over 3,900 K (3,600☌) for carbon. Solids are unlike liquids in that the intermolecular forces are strong enough to hold the particles in place. Describe the six different types of solids.Ī solid is like a liquid in that particles are in contact with each other.Describe the general properties of a solid.
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