Podcast
Questions and Answers
What does VSEPR stand for?
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion
What basic fact determines molecular shapes?
What basic fact determines molecular shapes?
Electron pairs repel each other.
What is the electronic geometry of NH3 (ammonia)?
What is the electronic geometry of NH3 (ammonia)?
Tetrahedral
Under what condition is the electronic arrangement the same as the molecular shape?
Under what condition is the electronic arrangement the same as the molecular shape?
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What is the molecular geometry of ammonia (NH3)?
What is the molecular geometry of ammonia (NH3)?
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Why is the bond angle of H2O less than 109.5˚?
Why is the bond angle of H2O less than 109.5˚?
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What is the arrangement of atoms around the central atom in a molecule with five covalent bonds and no lone pairs?
What is the arrangement of atoms around the central atom in a molecule with five covalent bonds and no lone pairs?
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True or False: All non-polar molecules have non-polar bonds.
True or False: All non-polar molecules have non-polar bonds.
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Which molecular geometry is possible with 0, 3, or 4 lone pairs?
Which molecular geometry is possible with 0, 3, or 4 lone pairs?
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Consider this molecule: HCN (with C as the central atom). The electronic geometry of this molecule is __________. The molecular geometry of this molecule is __________. This molecule is __________. There are/is __________ lone pair(s) total within the molecule.
Consider this molecule: HCN (with C as the central atom). The electronic geometry of this molecule is __________. The molecular geometry of this molecule is __________. This molecule is __________. There are/is __________ lone pair(s) total within the molecule.
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Consider this molecule: SCl4. The electronic geometry of this molecule is __________. The molecular geometry of this molecule is __________. This molecule is __________. There are/is __________ lone pair(s) on the central atom and there are/is __________ lone pair(s) total within the molecule.
Consider this molecule: SCl4. The electronic geometry of this molecule is __________. The molecular geometry of this molecule is __________. This molecule is __________. There are/is __________ lone pair(s) on the central atom and there are/is __________ lone pair(s) total within the molecule.
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The Valence Bond theory describes the bonds in molecules as arising from the __________ of atomic orbitals centered on the atoms in the molecule. However, to achieve the correct geometries, it must often use new __________ orbitals that result from the mixing of some number of pure atomic orbitals.
The Valence Bond theory describes the bonds in molecules as arising from the __________ of atomic orbitals centered on the atoms in the molecule. However, to achieve the correct geometries, it must often use new __________ orbitals that result from the mixing of some number of pure atomic orbitals.
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What type of geometry do new hybridized atomic orbitals occupy around the atom?
What type of geometry do new hybridized atomic orbitals occupy around the atom?
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How many other atoms can a central atom that is sp3 hybridized bind?
How many other atoms can a central atom that is sp3 hybridized bind?
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How many pi bonds can a central atom that is sp2 hybridized form with a neighboring atom that has a p orbital?
How many pi bonds can a central atom that is sp2 hybridized form with a neighboring atom that has a p orbital?
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What describes the bonds that exist between the two nitrogen atoms in the molecule N2?
What describes the bonds that exist between the two nitrogen atoms in the molecule N2?
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What is the hybridization of the second carbon atom in H2CCCH2?
What is the hybridization of the second carbon atom in H2CCCH2?
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What is the hybridization of the central atom if it has five regions of high electron density with one being a lone pair?
What is the hybridization of the central atom if it has five regions of high electron density with one being a lone pair?
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What is the hybridization of Sb in the molecule SbCl5^2-?
What is the hybridization of Sb in the molecule SbCl5^2-?
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Identify the orbitals used by the bolded atom in acetone (CH3COCH3).
Identify the orbitals used by the bolded atom in acetone (CH3COCH3).
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Using molecular orbital theory, we can calculate quantitatively the energy of a molecule as a function of the __________ between the two nuclei.
Using molecular orbital theory, we can calculate quantitatively the energy of a molecule as a function of the __________ between the two nuclei.
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Such calculations for the diatomic molecule would yield information about __________.
Such calculations for the diatomic molecule would yield information about __________.
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MOs (molecular orbitals) that are lower in energy than their corresponding AOs (atomic orbitals) are called __________. MOs that are higher in energy than their corresponding AO's are called __________. If the MOs have identical energy (or very similar energy) to the AOs, we label them as __________.
MOs (molecular orbitals) that are lower in energy than their corresponding AOs (atomic orbitals) are called __________. MOs that are higher in energy than their corresponding AO's are called __________. If the MOs have identical energy (or very similar energy) to the AOs, we label them as __________.
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What type of interference is responsible for sigma bonding?
What type of interference is responsible for sigma bonding?
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What are nodes?
What are nodes?
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What is the bond order of methane (CH4)?
What is the bond order of methane (CH4)?
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What can non-bonding orbitals be thought of as?
What can non-bonding orbitals be thought of as?
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What are the molecular orbital configurations for O2, O2-, and O2-- and their respective bond orders?
What are the molecular orbital configurations for O2, O2-, and O2-- and their respective bond orders?
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If you find a molecule absorbs wavelengths of 205 nm, 280 nm, and 310 nm, which corresponds to the HOMO-LUMO energy gap?
If you find a molecule absorbs wavelengths of 205 nm, 280 nm, and 310 nm, which corresponds to the HOMO-LUMO energy gap?
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What would you likely guess about an unknown molecular substance?
What would you likely guess about an unknown molecular substance?
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What is MO theory better at describing than VB theory?
What is MO theory better at describing than VB theory?
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What forces does every molecule have?
What forces does every molecule have?
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For which of the following molecules will dipole-dipole interactions be important? A. CO2 B. SO2 C. O2 D. O3
For which of the following molecules will dipole-dipole interactions be important? A. CO2 B. SO2 C. O2 D. O3
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Which of the following molecules can be involved in hydrogen bonding? H2, HF, CH4, CH3OH
Which of the following molecules can be involved in hydrogen bonding? H2, HF, CH4, CH3OH
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Which would you expect to have the lowest vapor pressure at room temperature?
Which would you expect to have the lowest vapor pressure at room temperature?
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Substances A and B are similar in size and weight, but substance A is more volatile than substance B. What can be true based on this information? (Select all that apply)
Substances A and B are similar in size and weight, but substance A is more volatile than substance B. What can be true based on this information? (Select all that apply)
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Rank the liquids in order of increasing viscosity at 25°C: I. C6H6 II. CH3CH2OH III. CH2OHCHOHCH2OH IV. CH2OHCH2OH V. H2O
Rank the liquids in order of increasing viscosity at 25°C: I. C6H6 II. CH3CH2OH III. CH2OHCHOHCH2OH IV. CH2OHCH2OH V. H2O
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What holds covalent solids together?
What holds covalent solids together?
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If a soluble ionic compound is made into an aqueous solution, what is usually observed?
If a soluble ionic compound is made into an aqueous solution, what is usually observed?
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What kind of materials conduct heat and electricity well in the solid state?
What kind of materials conduct heat and electricity well in the solid state?
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How would you classify the solid quartz (SiO2) which has a relatively high melting point?
How would you classify the solid quartz (SiO2) which has a relatively high melting point?
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Which type of crystalline solid is typically the most malleable?
Which type of crystalline solid is typically the most malleable?
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Study Notes
VSEPR Theory and Molecular Geometry
- VSEPR stands for Valence Shell Electron Pair Repulsion, where electron pairs repel each other, determining molecular shapes.
- NH3 has a tetrahedral electronic geometry but a trigonal pyramidal molecular geometry due to one lone pair on the nitrogen atom.
- H2O has a bond angle less than 109.5˚ because lone pair repulsion is greater than bonding pair repulsion.
- The arrangement for a central atom bonded to five atoms (with no lone pairs) is trigonal bipyramidal.
Molecular Geometry Concepts
- Non-polar molecules can have polar bonds, making the statement that all non-polar molecules have non-polar bonds false.
- A linear molecular geometry can occur with 0, 3, or 4 lone pairs on the central atom.
- For HCN, both electronic and molecular geometries are linear, and the molecule is polar with one lone pair.
Hybridization and Bonding
- Valence Bond theory states that bonds arise from the overlap of atomic orbitals and often require hybrid orbitals for correct geometries.
- sp³ hybridization allows a central atom to bond with up to four other atoms.
- A sp² central atom can form one pi bond with a neighboring atom with a p orbital.
- N₂ involves one sigma bond and two pi bonds between the nitrogen atoms, with each nitrogen being sp hybridized.
Molecular Orbital Theory
- Molecular orbitals (MOs) are classified as bonding, anti-bonding, or non-bonding depending on their energy relative to atomic orbitals.
- Sigma bonds result from constructive interference and are located "on axis" between two nuclei.
- Nodes represent regions of zero electron density in molecular interactions.
- For the molecules O2, O2-, and O22-, the bond orders are 2, 1.5, and 1, respectively.
Intermolecular Forces
- All molecules exhibit dispersion forces, and dipole-dipole interactions are significant in polar molecules like SO2 and O3.
- Hydrogen bonding occurs in HF and CH3OH, significant due to the strong interactions involving H and highly electronegative atoms.
- Compounds like CCl4 and CO2 are characterized by having only dispersion forces.
Vapor Pressure and Surface Tension
- CH4 has the lowest vapor pressure at room temperature, indicating stronger intermolecular forces in other substances.
- Higher volatility correlates with lower boiling points and weaker intermolecular forces.
- Surface tension phenomena include a piece of aluminum foil floating and water beading on a windshield.
Types of Solids
- Covalent solids, such as quartz (SiO2), are held together by covalent bonds and exhibit high melting points.
- Metallic solids are typically the most malleable due to the nature of metallic bonding.
- Ionic compounds in aqueous solutions conduct electricity, indicating the presence of free-moving ions.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge with these flashcards covering key concepts from Chemistry Unit 3. Explore important terms like VSEPR theory and molecular shapes, and understand how electron pairs influence molecular geometry. Perfect for students preparing for exams or wanting to strengthen their understanding of molecular structure.
