Chemistry Unit 6 Part 2

VSEPR theory

Valence Shell Electron Pair Repulsion theory predicts molecular shapes based on electron pair repulsion.

Molecular shape determination

The number of bonding and lone pairs around the central atom determines molecular shape.

Molecular geometry of 2 electron domains

Linear (e.g., CO₂) is the geometry of a molecule with 2 electron domains.

Molecular geometry with 3 bonding pairs and 0 lone pairs

Trigonal Planar (e.g., BF₃) is the geometry of such a molecule.

Molecular geometry with 3 electron domains and 1 lone pair

Bent (e.g., SO₂) is the geometry for this arrangement.

Molecular geometry with 4 bonding pairs and 0 lone pairs

Tetrahedral (e.g., CH₄) is the geometry for this configuration.

Molecular geometry with 4 electron domains and 1 lone pair

Trigonal Pyramidal (e.g., NH₃) describes this molecular geometry.

Molecular geometry with 5 electron domains

Trigonal Bipyramidal (e.g., PCl₅) is the geometry here.

Molecular geometry with 6 electron domains

Octahedral (e.g., SF₆) is the geometry of a molecule with 6 electron domains.

VSEPR notation

AXₙEₘ, where A = central atom, Xₙ = number of bonding atoms, Eₘ = number of lone pairs.

Hybridization

The mixing of atomic orbitals to form hybrid orbitals for bonding.

Hybridization of a linear molecule

sp is the hybridization for linear molecules.

Hybridization of a trigonal planar molecule

sp² is the hybridization for trigonal planar molecules.

Hybridization of a tetrahedral molecule

sp³ is the hybridization for tetrahedral molecules.

Hybridization of a trigonal bipyramidal molecule

sp³d is the hybridization for trigonal bipyramidal molecules.

Hybridization of an octahedral molecule

sp³d² is the hybridization for octahedral molecules.

Molecular polarity determination

Electronegativity differences and molecular shape determine molecular polarity.

Flowchart for molecular polarity

1. Are there polar bonds? If Yes, is the shape symmetrical? If Yes, Nonpolar; If No, Polar. If No, Nonpolar.

Nonpolar molecule shapes

Linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral shapes are usually nonpolar if all outer atoms are the same. Square planer.

Polar shapes

Bent, trigonal pyramidal, seesaw, T-shaped shapes are usually polar.

Bond angle of a linear molecule

180° is the bond angle for linear molecules.

Bond angle of a trigonal planar molecule

120° is the bond angle for trigonal planar molecules.

Bond angle of a tetrahedral molecule

109.5° is the bond angle for tetrahedral molecules.

Bond angle of a trigonal bipyramidal molecule

90° and 120° are the bond angles for trigonal bipyramidal molecules.

Bond angle of an octahedral molecule

90° is the bond angle for octahedral molecules.

Types of intermolecular forces

London Dispersion, Dipole-Dipole, Hydrogen Bonding are the three types.

London Dispersion Forces (LDFs)

Weak forces caused by temporary electron shifts present in all molecules, strongest in large nonpolar molecules.

Dipole-Dipole forces

Attractions between permanent dipoles in polar molecules.

Hydrogen Bonding

A strong dipole-dipole attraction specifically between H and N, O, or F.

Weakest intermolecular force

London Dispersion Forces are the weakest type of intermolecular force.

Strongest intermolecular force

Hydrogen Bonding is the strongest type of intermolecular force.

Dominant IMF in water (H₂O)

Hydrogen Bonding is the dominant intermolecular force in water.

Dominant IMF in CO₂

London Dispersion Forces dominate in CO₂ since it is nonpolar.

Dominant IMF in HCl

Dipole-Dipole forces are dominant in HCl, since it is polar but does not exhibit hydrogen bonding.