http://intro.chem.okstate.edu/1215/lecture/chapter7/lecture92898.html

All ionic compounds are solids in their standard state (25 degrees Celsius and 1 atmosphere). Ionic compounds are composed of ions; elements or molecules which are positively charged are called cations and elements or molecules which are negatively charged are called anions. A simple model to be used to imagine what ions (cations or anions) look like at the atomic level, is a sphere. For simple monoatomic ions and most polyatomic ions we can think of as charged spheres of different sizes.

In the state the spheres (ions) are arranged so that any particular ion is surrounded by the oppositely charged ion. What ever pattern which arises depends on several factors which we will not be discussing at this point in our class. Below is a picture of a model of a simple ionic compound. Notice the spheres (ions) of different sizes and how each sphere (ion) is surrounded by the other spheres (ion).

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What happens when an ionic compound dissolves in water? Below is a figure of a small crystal of sodium chloride surrounded by water molecules. We all know when sodium chloride is added to water the crystals of sodium chloride disappear, dissolve.

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What happens when the sodium chloride dissolves? Below is a picture showing a chloride ion (larger sphere) and a sodium ion (smaller sphere) dissolved in water.

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Notice how water surrounds (hydrates) each ion. For the negatively charged chloride ion the