Questions and Answers
What is VSEPR theory?
Valence shell electron pair repulsion theory is a model for predicting the molecular geometry of molecules based on the number of electron pairs around a central atom.
What is the bond angle in carbon dioxide and why?
180°
Use VSEPR theory to predict the molecular geometry around either carbon atom in acetylene, C2H2.
Linear
Use VSEPR theory to predict the molecular geometry of BrF5.
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Which of the following terms describe common molecular shapes? (Select all that apply)
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Which has the longest bond length?
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What are the approximate I-N-I bond angles in NI3?
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The shape of a molecule of NH3 is said to be?
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What is bond order?
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What is bond energy?
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What is bond length?
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Using the periodic table, rank the bonds in each set in order of decreasing bond length and decreasing bond strength: S-F, S-Br, S-Cl.
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Using the periodic table, rank the bonds in each set in order of decreasing bond length and decreasing bond strength: C=O, C-O, C≡O.
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What does V.S.E.P.R stand for?
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What is molecular shape?
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How is molecular shape classified?
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What is a bond angle?
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Study Notes
VSEPR Theory
- Valence Shell Electron Pair Repulsion (VSEPR) theory predicts molecular geometry based on electron pair repulsion.
- The shape of a molecule is determined by the number of electron pairs around a central atom.
Carbon Dioxide Bond Angle
- Carbon dioxide has a bond angle of 180° due to its linear arrangement (MX2) with two double bonds to oxygen.
Acetylene Molecular Geometry
- Acetylene (C2H2) has a linear geometry around each carbon atom because of the presence of a double bond.
BrF5 Geometry
- The molecular geometry of bromine pentafluoride (BrF5) is square pyramidal.
Common Molecular Shapes
- Six common molecular shapes include:
- Linear
- Trigonal Pyramidal
- Bent
- Trigonal Planar
- Tetrahedral
- Trigonal Bipyramidal
Bond Lengths and Types
- A single bond has the longest bond length compared to double and triple bonds.
- Bond length increases from triple to double to single bonds.
Nitrogen Triiodide (NI3) Bond Angles
- The I-N-I bond angles in nitrogen triiodide (NI3) are approximately 109.5°.
Unexpected Bond Angles
- A bond angle of 60° is not expected in any molecular structure.
Ammonia Shape
- The shape of ammonia (NH3) is described as pyramidal due to its nonbonding electron pair on nitrogen.
Polar Molecule Identification
- Water (H2O) is a polar molecule among the options given (CCl4, H2O, CO2, N2).
Most Polar Bond
- Hydrofluoric acid (HF) contains the most polar bond compared to HBr, HCl, and H2O.
Nonlinear Structures
- H2S is not a linear structure, unlike H-C≡C-H, I2, and CO2.
Central Atom Nonbonding Pairs
- Ammonia (NH3) has a nonbonding pair of electrons on the central nitrogen atom.
Bond Order
- Bond order signifies the number of shared electron pairs between two atoms; a single bond has a bond order of 1.
Bond Energy
- Bond energy is the energy required to break a bond, correlating with bond strength; stronger bonds exhibit higher bond energy.
Bond Length
- Bond length is defined as the distance between the nuclei of bonded atoms.
Periodic Table Bond Ranking (S Bonds)
- For S-F, S-Br, S-Cl:
- Bond length: S-Br > S-Cl > S-F
- Bond strength: S-F > S-Cl > S-Br
Periodic Table Bond Ranking (C Bonds)
- For C=O, C-O, C≡O:
- Bond length: C-O > C=O > C≡O
- Bond strength: C≡O > C=O > C-O
VSEPR Abbreviation
- V.S.E.P.R stands for Valence-Shell Electron-Pair Repulsion Theory.
Molecular Shape
- Molecular shape refers to the three-dimensional arrangement of nuclei linked by bonding groups, focused on relative positions.
Molecular Shape Classification
- Classified using the notation MXaEb where:
- M = central atom
- X = surrounding atom
- E = nonbonding valence-electron group
- a and b are integers representing their quantities.
Bond Angle Definition
- Bond angle is the angle formed by the nuclei of two surrounding atoms relative to the nucleus of the central atom.
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Test your knowledge on molecular geometry concepts with these flashcards. Learn about VSEPR theory and bond angles in molecules such as carbon dioxide. Perfect for students studying chemistry.