Molecular Structures &
Polarity
SCH3U1
Matter, Chemical Trends &
Chemical Bonding
In the most acceptable electrondot structure for carbonyl
fluoride, COF2 the central atom is
A) C, which is singly-bonded to O.
B) C, which is doubly-bonded to O.
C) O, which is singly-bonded to C
D) O, which is doubly-bonded to C.
In the most acceptable electrondot structure for carbonyl
fluoride, COF2 the central atom is
A) C, which is singly-bonded to O.
B) C, which is doubly-bonded to O.
C) O, which is singly-bonded to C
D) O, which is doubly-bonded to C.
Recall: the concept of
ELECTRONEGATIVITY
Polar Covalent Bonds and
Electronegativity
Electronegativity (EN) is a measure of the ability of an
atom to attract its bonding electrons to itself.
EN is related to ionization energy and electron affinity.
The greater the EN of an atom in a molecule, the more
strongly the atom attracts the electrons in a covalent
bond.
Electronegativity generally
increases from left to right
within a period, and it
generally increases from the
bottom to the top within a
group.
Pauling’s Electronegativities
It would be a good idea to
remember the four elements of
highest electronegativity: N, O, F,
Cl.
A reactive element with a
relatively high electronegativity
would be expected to have a
relatively
A) small negative electron affinity and
a relatively low ionization energy.
B) small negative electron affinity and
a relatively high ionization energy.
C) large negative electron affinity and
a relatively low ionization energy.
D) large negative electron affinity and
a relatively high ionization energy.
A reactive element with a
relatively high electronegativity
would be expected to have a
relatively
A) small negative electron affinity and
a relatively low ionization energy.
B) small negative electron affinity and
a relatively high ionization energy.
C) large negative electron affinity
and a relatively low ionization
energy.
D) large negative electron affinity and
a relatively high ionization energy.
Electronegativity Difference
and Bond Type
Identical atoms have the same electronegativity and
share a bonding electron pair equally. The bond is a
nonpolar covalent bond.
When electronegativities differ significantly, electron pairs
are shared unequally.
The electrons are drawn closer to the atom of higher
electronegativity; the bond is a polar covalent bond.
With still larger differences in electronegativity, electrons
may be completely transferred from metal to nonmetal
atoms to form ionic bonds.
Electronegativity Difference
and Bond Type
No sharp cutoff
between ionic and
covalent bonds.
Cs—F bonds are “so
polar” that we call the
bonds ____.
C—H bonds are
virtually nonpolar.
The compound ICl contains
A) ionic bonds.
B) non-polar covalent bonds.
C) polar covalent bonds, with partial
negative charges on the Cl atoms.
D) polar covalent bonds, with partial
negative charges on the I atoms.
The compound ICl contains
A) ionic bonds.
B) non-polar covalent bonds.
C) polar covalent bonds, with
partial negative charges on the
Cl atoms.
D) polar covalent bonds, with partial
negative charges on the I atoms.
Based on their
electronegativities, arrange the
following in order of increasing
ionic character:
CsBr, LaBr3, PBr3, MgBr2.
A) CsBr, LaBr3, MgBr2, PBr3
B) CsBr, MgBr2, PBr3, LaBr3
C) PBr3, LaBr3, MgBr2, CsBr
D) PBr3, MgBr2, LaBr3, CsBr
Based on their
electronegativities, arrange the
following in order of increasing
ionic character:
CsBr, LaBr3, PBr3, MgBr2.
A) CsBr, LaBr3, MgBr2, PBr3
B) CsBr, MgBr2, PBr3, LaBr3
C) PBr3, LaBr3, MgBr2, CsBr
D) PBr3, MgBr2, LaBr3, CsBr
Polar Covalent Bonds and
Dipole Moments
Polar Covalent Bonds and
Dipole Moments
C-Cl bond has a bond dipole because of
a difference in electronegativities.
Polar Covalent Bonds and
Dipole Moments
Polar Covalent Bonds and
Dipole Moments
The individual bond polarities do not cancel.
Therefore, the molecule has a dipole
moment. In other words, the molecule is
polar.
Polar Covalent Bonds and
Dipole Moments
The individual bond polarities cancel.
Therefore, the molecule does not have a
dipole moment. In other words, the molecule
is nonpolar.
Which covalent bond is
the most polar?
A) N-F
B) C-F
C) Cl-F
D) F-F
Which covalent bond is
the most polar?
A) N-F
B) C-F
C) Cl-F
D) F-F
Which of the following
molecules does NOT
have a dipole moment?
A)
B)
C)
D)
CH2=CH2
NH3
CH3NH2
HCl
Which of the following
molecules does NOT
have a dipole moment?
A)
B)
C)
D)
CH2=CH2
NH3
CH3NH2
HCl
Which of the following
should be the most
polar?
A)
B)
C)
D)
H2 (g)
CO2 (g)
KCl (g)
CH3F (g)
Which of the following
should be the most
polar?
A)
B)
C)
D)
H2 (g)
CO2 (g)
KCl (g)
CH3F (g)