UTF-8Activity Title: Page 6240233207111org.concord.modeler.text.LineIcon750.03010105<html>
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<strong>An Overview of Chemical Elements </strong>
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The Chemistry of the Electronics Industry
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What is a semiconductor?
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<strong>Metalloids, shown in purple on the periodic table,
exhibit characteristics of both metals and nonmetals. Silicon,
for example, possesses a metallic luster, yet it is an
inefficient conductor and is brittle. The reactivity of the
metalloids depends on the element with which they are reacting.
For example, boron acts as a nonmetal when reacting with sodium
yet as a metal when reacting with fluorine. The boiling points,
melting points, and densities of the metalloids vary widely. The
intermediate conductivity of metalloids means they tend to make
good semiconductors. </strong>
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<img src="periodic-table.gif">
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falseLine11org.concord.modeler.PageMultipleChoicetrue4500200<html>
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Which of the following is not true of metalloids?
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trueTheir properties fall between those of metals and those of nonmetals.They fall to the left of the periodic table.They make good semiconductors.They fall between metals and nonmetals on the periodic table.1falseLine111org.concord.modeler.PageTextBox575.0425.0<html>
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<strong>Some materials, such as silicon crystals, do not conduct
electricity well at very low temperature. Because silicon has four outer
electrons, a silicon atom shares its electrons with four other silicons
to give each atom eight outer electrons, or a complete outer shell.
These electrons are tightly bound to silicon atoms and behave like those
in insulators. But when temperature increases, some electrons become
loose and can "hop" from one atom to another leaving a vacancy in the
bond known as a "hole" that other electrons can fill. This allows for
the movement of electrons which results in an electric current.<br><br>This
simulation shows how electrons move in a silicon crystal at different
temperatures. The gray shapes show the sharing of electrons between
silicon atoms. The dashed circles show the electron positions in the
bonds. When they are not occupied by an electron, they represent a hole.<br><br>Instructions:<br>1)
Click the "Run" button and observe what happens.<br>2) Pull
the "Temperature" slider to increase the temperature in small increments
and observe the movement of electrons and the ammeter at each step.</strong>
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falseLineorg.concord.mw2d.activity.AtomContainerpage6$0.mml1org.concord.modeler.PageButtonRunRunfalseorg.concord.mw2d.models.MolecularModel0Execute MW scriptorg.concord.modeler.PageButtonStopStopfalseorg.concord.mw2d.models.MolecularModel0Execute MW scriptorg.concord.modeler.PageButtonResetResetfalseorg.concord.mw2d.models.MolecularModel0Execute MW scriptorg.concord.modeler.PageSliderorg.concord.mw2d.models.MolecularModel0300.00.05000.050Temperature20060falsetrueTemperature1org.concord.modeler.PageTextArea400150<html>
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At low temperature, would you say the silicon crystal conducts
electricity? Explain.
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What happens to the electrons as the temperature increases and how does
this affect the electrical conductivity? (Include evidence from the
model to support your answer.)
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Summarize how atomic structure affects electrical conductivity between
conductors, insulators and semiconductors.
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In your own words, explain under what conditions a semiconductor may
become an electical conductor and how this occurs in terms of the
electrons.
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