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Polar Covalent Bonds
The bonding electrons are attracted more strongly by one atom than the other so that the electron distribution between atoms is not symmetrical
The intrinsic ability of an atom to attract the shared electrons in a covalent bond
Most Electronegative
Least Electronegative
polar covalent electronegativity
Nonpolar covalent bond electronegativity
Differ less than 0.5
Ionic electronegativity
differ by more than 2
bond polarity crossed arrow --I--------->
electrons are displaced in the direction of the arrow

Head of arrow (--I--) is electron poor (δ+)

Tail of arrow (----) is electron rich (δ-)
Electrostatic Potential Maps
Use color to indicate electron rich (red-δ-) and electron poor (blue-δ+)
Inductive Effect
Shifting of electons in a σ bond in resoinse to the electronegativity of nearby atoms
Dipole Moment (μ)
the magnitude of the charge Q at either end of the molecular dipole times the distance r between the charges 


Expressed in debyes (D) 

1D=3.336x10-30 coulomb meter (C·m)
Formal charge
the number of valence electrons in a neutral, isolated atom minus the number of electrons owned by the bonded atom in a molecule
Individual resonance forms are imaginary not real
The real structure is a composite or resonance hybrid of the differnt forms.
Resonance forms only differ in the
placement of their Π bonds or nonbonding electrons
Curved arrows on resonance structures
indicate the movement of electrons, not the movement of the atoms
different resonance forms of a substance doesn't have to
be equivalent
Resonance forms obey
Normal valency rules
The resonance hybrid is
more stable than any individual resonance form
Resonance leads to
Any 3 atom grouping with a p orbital on each atom has
2 resonance forms
organic acids
have a positively polarized hydrogen atom and have either a hydrogen bonded to an electronegative oxygen or contain a hydrogen bonded to a carbon that is next to a carbon oxygen double bonded. H-O H-C=O
bronsted-lowry acid
substance that donates H+ ions
bronsted-lowry base
a substance that accepts. H+ ions
acid dissociation equilibrium
as pka gets smaller
acid strength gets larger
organic base
presence of an atom with a lone pair that can bond to H+. most common are nitrogen containing compounds.
Lewis acid
a substance that accepts an electron pair
Lewis base
a substance that donated an electron pair
dipole-dipole forces
noncovalent interaction....occur between molecules as a result of electrostatic interaction among dipoles attractive when unlike charges are together repulsive when like charges are together
dispersion forces
occur between all neighboring molecules and arise because the electron distribution within molecules is constantly changing may cause a temporary dipole moment which causes nearby molecules to adapt a temporary dipole ..... can be strong enough to hold substances together.
hydrogen bond
an attractive interaction between a hydrogen bonded to an oxygen or nitrogen and an unshared electron pair on another oxygen or nitrogen. represented by dotted line
water loving usually have a number of ionic charges or polar -OH groups so they can form hydrogen. bonds
water fearing do not have groups that form hydrogen bonds only force in water is weak dispersion forces
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