Transcript Does the image show ionic or covalent bonding? Support your

Does the image show ionic or covalent bonding? Support
your answer.
http://www.powayusd.com/pusdphs/webquests/chemwebquest/chemsite.htm
Objective
• Describe the difference between ionic
bonds and covalent bonds.
Lab
• Pre-questions
• Lab setup
• When you finish your lab, clean up your
station and return to your seat. Begin
working on the post-lab questions.
Post-Lab Discussion
• Why is distilled water used for this lab
instead of just tap water? (hint: think about
what is in tap water)
– Tap water contains impurities (other
substances besides hydrogen and oxygen).
Many of these substances are ions, which will
conduct electricity.
– Had we used tap water, our sugar solution
could have conducted electricity – providing
misleading results.
Post-Lab Discussion
• What properties in general do covalentbonded substances have?
– Low melting/boiling points – evidenced by
sugar melting in our flame test.
– Poor conductors of electricity – evidenced by
lack of bubbles in battery test.
Post-Lab Discussion
• What properties in general do ionicbonded substances have?
– High melting/boiling points – evidenced by
lack of salt melting in our flame test. (salt has
a melting point of 800oC!!)
– Good conductors of electricity – evidenced by
production of bubbles in battery test. (bubbles
are result of H2 gas production)
Post-Lab Discussion
• Which compound melted most easily? Is it
ionic or covalent?
– Sugar – covalent
Post-Lab Discussion
• Using the periodic table explain how the
position of the elements that make up
sugar (C12H22O6) and Ethanol (C2H5OH)
can be used to tell if the bonds are ionic or
covalent.
– Located on right-hand side (except Hydrogen)
– Non-metals
Post-Lab Discussion
• Using the periodic table explain how the
position of the elements that make up salts
NaCl, CaCl2, KCl) can be used to tell if the
bonds are ionic or covalent.
– Located on opposite sides of periodic table.
– Non-metal bonding with a metal.
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond2.html
Electronegativity
Definition:
Term:
Attraction an atom has for a shared pair of
electrons in a chemical bond.
Electronegativity
Characteristics:
In my own words:
•Fluorine is most electronegative element
•Increases diagonally to the right on periodic table
•As you move down a group, electronegativity
decreases.
•Elements with the greatest difference in
electronegativity form strongest ionic bonds.
Write the definition of electronegativity in your
own words
Mine: ability of an atom to attract an electron.
Image of Electronegativity
Properties of Ionic Bonds
• Electronegativity difference > 2.
• Typically a bond between metal and a
nonmetal.
• Conduct Electricity.
• High melting/boiling points.
Properties of Covalent Bonds
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•
•
•
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Electronegativity difference < 2.
Typically a bond between 2 nonmetals.
Do Not Conduct Electricity.
Low melting/boiling points.
Polar Covalent – unequal sharing of
electrons.
• Covalent – equal sharing of electrons.
Oxidation Number
• Definition: indicates how many electrons
are lost, gained, or shared when bonding
occurs.
– Note: charge is written after the number
• Aligned with valence electrons
• Some atoms have more than one
oxidation number
Chemical Formulas
• Tell us how many atoms are in each
molecule
• Charge always equals 0
• Criss-Cross method
Writing Formulas
• Positive ion always comes first, then your
negative
– Na+ Cl• NaCl
Chemical Bonding Worksheet
• You will work with a partner to complete
the worksheet.
• You will make a model of your atom using
Fruity Pebbles as valence electrons.
• You MUST then draw your atom with its
valence electrons and show which
electrons are moving or being shared.