34 Questions
What is a characteristic of a more important resonance structure?
Adjacent atoms do not have similar formal charges
What is a condition for a resonance structure to be more important?
Formal charges are close to zero
What is a factor that determines the importance of a resonance structure?
Electronegativity of atoms
What is the purpose of calculating formal charges?
To evaluate the importance of resonance structures
What is a characteristic of a neutral molecule?
Formal charges are close to zero
Which of the following factors does not affect the importance of a resonance structure?
Bonding energy
What is the purpose of drawing resonance structures?
To evaluate the importance of resonance structures
What determines the magnetic property of a molecule?
Number of unpaired electrons
What determines the preferred resonance structure of an element?
The number of formal charges
What is the general rule for elements in the third period and beyond?
They prefer a structure that obeys the octet rule
What is a characteristic of the given structure?
It has fewer formal charges
What is the relationship between formal charges and resonance structures?
A structure with fewer formal charges is preferred
Why is structure (b) considered the most important?
Because the negative charge is on the more electronegative oxygen atom.
What is the conditions under which an expanded octet is preferred?
When it bears fewer formal charges
What is a characteristic of a resonance structure that is preferred?
It bears fewer formal charges
Which of the following is true about structure (c)?
It has a larger separation of formal charges.
What is the charge on the sulfate ion?
2–
How many oxygen atoms are bonded to the central S atom in the sulfate ion?
4
Which of the following is a characteristic of the sulfate ion?
It has a negative charge.
What is the source of the information about the sulfate ion?
Chang, 2010
What is the molecular structure of ClF3?
T-shaped
What is the hybridization of the central atom in ClF3?
sp3d
What is the number of bond pairs in ClF3?
3
What is the number of lone pairs on the central atom in ClF3?
2
Is ClF3 a polar or nonpolar molecule?
Polar
What is the shape of the molecule ClF3?
T-shaped
What is the reason for the increase in London forces with molar mass?
The molecules have more electrons, and dispersion forces increase in strength with the number of electrons
What is the relationship between the number of electrons in a molecule and its melting point?
The melting point increases as the number of electrons in the molecule increases
What is the trend observed in the boiling points of hydrogen compounds of Group 14?
The boiling point increases as the molar mass increases
Why do larger atoms have a more easily disturbed electron distribution?
Because their outer electrons are less tightly held by the nuclei
What is the relationship between the molar mass of a molecule and its electron distribution?
The electron distribution is more easily disturbed at higher molar masses
Which of the following compounds has the highest boiling point?
SnH4
What happens to the strength of dispersion forces as the number of electrons in a molecule increases?
The strength of dispersion forces increases
Why do compounds with larger molar mass tend to have higher melting points?
Because they have more electrons and increased dispersion forces
Study Notes
Resonance Structures
- A resonance structure is more important when adjacent atoms do not have similar formal charges.
- Electronegative atoms bearing negative formal charges make a resonance structure more important.
- Formal charges on atoms being close to zero for neutral molecules makes a resonance structure more important.
- The number of unpaired electrons being consistent with the magnetic property of the species makes a resonance structure more important.
Sample Problem 1: Nitrous Oxide
- Draw three resonance structures for the molecule nitrous oxide (NNO).
- Structure (b) is the most important because the negative charge is on the more electronegative oxygen atom.
- Structure (c) is the least important because it has a larger separation of formal charges and the positive charge is on the more electronegative oxygen atom.
Sample Problem 2: Sulfate Ion
- Draw a Lewis structure for the sulfate ion (SO42–) in which all four O atoms are bonded to the central S atom.
- The structure involves an expanded octet on S but may be considered more plausible because it bears fewer formal charges.
General Rule for Elements
- A resonance structure that obeys the octet rule is preferred over one that involves an expanded octet but bears fewer formal charges.
Sample Problem 3: ClF3
- Draw the Lewis structure of ClF3 and classify as polar or nonpolar.
Intermolecular Forces
- London forces usually increase with molar mass because molecules with larger molar mass tend to have more electrons, and dispersion forces increase in strength with the number of electrons.
- Larger molar mass often means a bigger atom whose electron distribution is more easily disturbed because the outer electrons are less tightly held by the nuclei.
- As expected, melting point increases as the number of electrons in the molecule increases.
- Hydrogen compounds of Group 14 follow the trend of increasing boiling point with increasing molar mass.
This quiz covers resonance structures in chemistry, including factors that make them more important and how adjacent atoms and electronegative atoms affect formal charges.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
