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11:18 AM
Page 260
A hot pool in Yellowstone
Park’s Upper Geyser Basin.
These pools are often
characterized by their
striking colors.
compounds. These compounds, such as potassium chloride, replace
the ions lost during physical activity.
Mineral hot springs, like those found in Yellowstone National
Park, are another example of ionic solutions. Many of the ionic
compounds dissolved in these hot springs contain the element sulfur.
Sulfur can have an unpleasant odor. The white deposits around the
pool come from the sulfur.
Covalent compounds have almost the opposite properties
of ionic compounds. Melting or boiling a covalent compound does
not require breaking chemical bonds. Therefore, covalent compounds
often melt and boil at lower temperatures than ionic compounds.
Unlike ionic compounds, molecules stay together when dissolved
in water. Therefore, covalent compounds are poor conductors of
electric charge. Table sugar, for example, does not conduct an electric
current when in solution.
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Find out more about the
properties of ionic and
covalent compounds.
Bonds can make the same element
look different.
Covalent bonds do not always form small individual molecules. This
explains how the element carbon can exist in three very different
forms—diamond, graphite, and fullerene. The properties of each
depend on how the carbon atoms are bonded to each other.
Diamond is the hardest natural substance. This property makes
diamond useful for cutting other substances. Diamonds are made
entirely of carbon. Each carbon atom forms covalent bonds with four
other carbon atoms. The pattern of linked atoms extends throughout
the entire volume of a diamond crystal. This three-dimensional
structure of carbon atoms gives diamonds their strength—diamonds
do not break easily.
260 Unit 3: Chemical Interactions
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