Chemical Bonding Theories and Hybridization

These flashcards cover key principles of chemical bonding theories, hybridization, and types of crystalline solids based on lecture notes.

What does the Lewis model represent?

Chemical bonds using an electron dot formula.

What major limitation does the Lewis model have?

It fails to explain the formation of chemical bonds and the shapes of polyatomic molecules.

What theory provides the geometry of simple molecules?

VSEPR theory.

What bonding theories explain covalent bonds accurately?

Valence bond theory and molecular orbital theory.

What does the valence bond (VB) theory assume?

Electrons occupy atomic orbitals of individual atoms during bond formation.

How does molecular orbital (MO) theory explain bonding?

It assumes the formation of molecular orbitals from atomic orbitals.

What is the basic principle of valence bond theory?

A covalent bond forms when orbitals of two atoms overlap and occupy the overlap region.

What is the significance of the overlap region in VBT?

It is where a pair of electrons is shared between the two nuclei.

How do hydrogen atoms form H2 molecules according to VBT?

Two H atoms' 1s orbitals overlap, forming a covalent bond.

What affects bond strength according to VBT?

The extent of overlap between orbitals.

What is a sigma bond (σ)?

A localized bond resulting from end-to-end overlap of atomic orbitals.

How do pi bonds (π) form?

Through sideways overlap of p orbitals.

What characterizes a single bond?

It consists of one σ bond.

What defines a double bond?

One σ bond and one π bond.

What is the geometry of a molecule with sp hybridization?

Linear.

What is hybridization in chemistry?

An imaginary mixing process of atomic orbitals to form new hybrid orbitals.

What type of hybridization occurs in methane (CH4)?

sp3 hybridization.

What angle do sp3 hybrid orbitals form?

109.5 degrees.

What is the shape of NH3 due to sp3 hybridization?

Pyramidal.

What is the bond angle in NH3?

107 degrees.

What is the shape of H2O due to hybridization?

V-shape or angular geometry.

What determines the bond angle in water compared to ammonia?

Lone pairs of electrons exert more repulsion than bond pairs.

What is the hybridization of phosphorus in PCl5?

sp3d hybridization.

What geometrical arrangement do sp3d hybrid orbitals achieve?

Trigonal bipyramidal.

What is the ideal bond angle for equatorial bonds in PCl5?

120 degrees.

What is the bond angle for axial bonds in PCl5?

90 degrees.

What is the hybridization in SF6?

sp3d2 hybridization.

What does MO theory assume about atomic orbitals?

They transform into new molecular orbitals upon overlap.

What are bonding molecular orbitals?

Molecular orbitals with increased electron density between nuclei.

What are antibonding molecular orbitals?

Molecular orbitals with a region of zero electron density between nuclei.

What is a bond order in molecular orbital theory?

The number of electrons in bonding MOs minus those in antibonding MOs, divided by two.

What is indicated by a bond order greater than zero?

The molecule is stable relative to the separate atoms.

What do all crystalline solids have in common?

A well-defined, ordered structure in three dimensions.

What is the difference between ionic and molecular crystals?

Ionic crystals consist of ions held together by ionic bonds, while molecular crystals consist of discrete molecules held by intermolecular forces.

What type of bonding holds metallic crystals together?

Strong metallic bonding forces.

What is the typical property of covalent network solids?

High melting and boiling points due to strong covalent bonds.

What is an example of a molecular crystal?

Ice or sugar.

What do metallic solids have that enhances their conductivity?

Delocalized electrons in a sea of electrons.