Resonance Structures (9.3.1) Flashcards
• Resonance structures are needed when more than one Lewis dot structure is
possible.
• Resonance structures are needed when more than one Lewis dot structure is
possible.
• Resonance structures can contribute equally or unequally to the overall structure
of the molecule.
• Resonance structures can contribute equally or unequally to the overall structure
of the molecule.
Resonance structures are needed when more than
one Lewis dot structure is possible.
In the example of ozone, the double bond can be
between the central and the right-hand atom, or
between the central and the left-hand atom. There
is more than one valid Lewis dot structure for ozone.
Each of these resonance structures satisfies the
octet rule for each of the atoms but they predict an
uneven geometry in the bonds.
In fact, both structures contribute to the structure of
the ozone molecule. Taken together they form a
more complete model of the molecule than either
would individually.
Resonance structures can contribute equally or
unequally.
In the examples shown, the nitrate ion has three
equivalent resonance structures that contribute
equally to the overall structure of the ion. In
contrast, the sulfur dioxide has two equivalent
resonance structures and a third non-equivalent
resonance structure. Nitrous oxide has three
inequivalent resonance structures. The nonequivalent
resonance structure contributes
differently to the overall structure than the other two.
In the case of sulfur dioxide, because of the ability
of sulfur to have an expanded octet the third
resonance structure is present when sulfur has ten
electrons.
In resonance structures the nuclei do not change
position, nor do the connections between nuclei
change; only the electrons move around.
Resonance structures are needed when more than
one Lewis dot structure is possible.
In the example of ozone, the double bond can be
between the central and the right-hand atom, or
between the central and the left-hand atom. There
is more than one valid Lewis dot structure for ozone.
Each of these resonance structures satisfies the
octet rule for each of the atoms but they predict an
uneven geometry in the bonds.
In fact, both structures contribute to the structure of
the ozone molecule. Taken together they form a
more complete model of the molecule than either
would individually.
Resonance structures can contribute equally or
unequally.
In the examples shown, the nitrate ion has three
equivalent resonance structures that contribute
equally to the overall structure of the ion. In
contrast, the sulfur dioxide has two equivalent
resonance structures and a third non-equivalent
resonance structure. Nitrous oxide has three
inequivalent resonance structures. The nonequivalent
resonance structure contributes
differently to the overall structure than the other two.
In the case of sulfur dioxide, because of the ability
of sulfur to have an expanded octet the third
resonance structure is present when sulfur has ten
electrons.
In resonance structures the nuclei do not change
position, nor do the connections between nuclei
change; only the electrons move around.
How many resonance structures can be drawn for a molecule whose structure is best explained by three different Lewis dot structures?
3 (C)
Which structure of the sulfate anion, [SO4 ]2−, is not equivalent to the other three?
(A)
This structure has only 8 octet electrons drawn for the sulfur atom, whereas the other structures have 12. This structure also has only single bonds between the sulfur atom and the oxygen atoms, whereas the other structures have double bonds between the sulfur atom and 2 of the oxygen atoms.
Which structure of phosphoric acid, H3PO4, is not equivalent to the other three?
(C)
This structure has only 8 octet electrons drawn for the phosphorus atom, whereas the other structures have 10. This structure also has only single bonds between the phosphorus atom and the oxygen atoms, whereas the other structures have a double bond between the phosphorus atom and one of the oxygen atoms.
Which of the following is not a reasonable resonance structure for the [ NCO]− anion in which the carbon atom is the central atom?
(A)
This is not a reasonable resonance structure for an [ NCO]− anion in which the carbon atom is the central atom. The order of the atoms was changed so that the oxygen atom is the central atom.
Which structure of the phosphite anion, [PO3 ]3−, is not equivalent to the other three?
(C)
This structure has only 8 octet electrons drawn for the phosphorus atom, whereas the other structures have 10. This structure also has only single bonds between the phosphorus atom and the oxygen atoms, whereas the other structures have a double bond between the phosphorus atom and one of the oxygen atoms.
Which structure of sulfuric acid, H2SO4, is not equivalent to the other three?
(D)
This structure has only 8 octet electrons drawn for the sulfur atom, whereas the other structures have 12. This structure also has only single bonds between the sulfur atom and the oxygen atoms, whereas the other structures have double bonds between the sulfur atom and 2 of the oxygen atoms.
Which statement about resonance hybrids is correct?
(B)
Each resonance structure contributes to describing a molecule’s stricture. However, when taken together, the resonance hybrid forms a better description of the molecule.
For which of the following molecules is it possible to draw resonance structures?
NO3- (B)
Which of the following is not a valid Lewis dot structure for hydrogen azide, HN3?
(D)
Although the correct total number of valence electrons is drawn, the Lewis dot structure is incorrect because the nitrogen atom that is bonded to the other 2 nitrogen atoms has 12 valence electrons instead of 8.
Which of the following is not a resonance structure for the azide anion, [ N3 ]−?
(B)
Although the correct total number of valence electrons is drawn, the Lewis dot structure is incorrect because the nitrogen atom that is bonded to the other 2 nitrogen atoms has 12 valence electrons instead of 8.
