Electronegativity and Chemical Bonding · Bonding Notes sb.notebook 1 April 18, 2013...
Transcript of Electronegativity and Chemical Bonding · Bonding Notes sb.notebook 1 April 18, 2013...
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Electronegativity and Chemical Bonding
To see how polar, nonpolar, or ionic a compound is, you have to look at the electronegativity difference.
Electroneg Difference Type of Bond0.0 0.3 Covalent (nonpolar) 2 nonmetals0.31 1.6 Covalent (polar)> 1.61 Ionic (Metal & Nonmetal)
How to Draw a Lewis Structure: dots and dashes around the element symbol(s) (nuclei) to show the bonding pattern.
Step 1: Determine type and number of atoms in the moleculeStep 2: Draw electron dot structures for each type of atomStep 3: Determine total # of valence electrons combinedStep 4: Arrange atoms to form a skeleton structure
(Usually the least electronegative atom goes in the middle) [Connect the dots!!]
Step 5: Count all electrons and make sure they equal the right amount of valence electrons.
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_08&folder=bonding
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_08&folder=lewis_structures
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Example A: Hydrogen Sulfide
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Example B: Ammonia
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
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Polar vs. NonpolarUnequal Dstn of charge = dstn of charge
United atoms have an unequal Bonding electrons are attraction for the shared electron shared equally by the bonded atoms
Happens when there is a bondbetween significantly electroneg. different atomsMolecular Shape
VSEPR Model
Shape of molecule matters determines if other molecules will react with it
Model is based on minimizing repulsions of shared and unshared pairs of electrons around the central atom.
Shared electron pairs repel one another
Lone pairs determine shape; have a slightly larger orbital than shared electrons.
Shared bonding orbitals are pushed together slightly by lone pairs.
Covalent Bonding
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WaterLewis Structure:
VSEPR Structure:
VSEPR Shapes
Bent
Pyramidal
Tetrahedral
Planar
Linear
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Odds and Ends.........
Electron Affinity similar to electronegativity
You can have a polar bond but not necessarily a polar molecule.
If there is a nonpolar bond (based on electronegativities), then it is a nonpolar molecule Symmetrical (mirror image) = Nonpolar molecule If there is a polar bond
No symmetry = Polar Molecule
Remember that like dissolves like. If you have a grease stain on your shirt and you throw it in the wash, will Tide (regular detergent) get the stain out??? Why or why not????
Polar molecules and ionic compounds are usually soluble in polar substances
Van der Waals forces (Intermolecular Forces)= weak forces of attraction between individual molecules
Many physical properties of covalent molecular solids are due to this (ex: melting & boiling points)
Bond length decreases with each addition of a multiple bond.
The shorter the bond, the stronger it is.
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Resonance
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_08&folder=resonance
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http://www.ucalgary.ca/~ntaucoin/VSEPRtable.pdf
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VSEPR Problems
http://bertrand.home.mindspring.com/chem/vsframe.htm
http://www.chem.purdue.edu/gchelp/vsepr/contents.html
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