Polarity of Bonds and Molecules Mrs. Huelin Chemistry April 24, 2012.
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Transcript of Polarity of Bonds and Molecules Mrs. Huelin Chemistry April 24, 2012.
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Polarity of Bonds and Molecules
Mrs. Huelin ChemistryApril 24,
2012
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Polarityof bonds …HCl
H2O
of molecules …H2O
CO2
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For each molecule, draw the Lewis structure, predict the shape and bond angle, and identify as polar or nonpolar. Br2
HCN
C2H2
NH4+
H2S
PF3
CH2O
MgO
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Electronegativity differences indicate Polarity
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Electronegativity difference (∆En) and Bond type
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For each pair of elements, calculate the electronegativity difference and label the bond type (polar covalent, nonpolar covalent, or ionic).H, ClH, SS, ClNa, FCl, BrAl, Br
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Energy Practice Problem
Given the following bond dissociation energy values, calculate the total energy that would be required to break all of the covalent bonds in 0.25 mol of ethane (C2H6).
C-C = 347 kJ/molC-H = 393 kJ/mol
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VIDEO LESSONWater, a polar molecule, on YouTube:
http://www.youtube.com/watch?v=DVCYlST6mYQ
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REVIEWIonic and Covalent Compounds
Practice Quiz and Graphics: http://www.elmhurst.edu/~chm/vchembook/145Areview.html
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Internet resourcesMolecular polarity:
http://www.elmhurst.edu/~chm/vchembook/210polarity.html
Polar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/152Apolar.html
Nonpolar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/150Anpcovalent.html
Ionic compounds: http://www.elmhurst.edu/~chm/vchembook/143Aioniccpds.html
Compare Ionic, Polar, and Nonpolar Bonds: http://www.elmhurst.edu/~chm/vchembook/153Acompare.html
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Properties of Covalent CompoundsLow melting and boiling points
(melting sugar, not salt)Many exist as gases or vaporize
readily at room temperature (oxygen, carbon dioxide)
Form relatively soft solids (paraffin wax)
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Forces of Attraction Intramolecular
forces (bonding forces)
Covalent bond is strong (sharing of electrons)
Covalent network solids = brittle, nonconductors, extremely hard, very high melting point (diamond, quartz)
Intermolecular forces (a.k.a. van der Waals forces)
Dispersion (induced dipole) = between nonpolar molecules
Dipole-dipole = between polar molecules
Hydrogen bond = between hydrogen on one molecule and fluorine, oxygen, or nitrogen on another
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Multiple Choice Review1. Which
substance contains both covalent and ionic bonds?
a) NH4NO3
b) CH3OCH3
c) LiFd) CaCl2
2. Which of these bonds is most polar?
a) H-Clb) H-Brc) H-Fd) H-I
3. Which of these molecules can form a hydrogen bond with a water molecule?
a) N2
b) NH3
c) O2
d) CH4