Chemical Bonding II: Molecular Geometry and Hybridization of Atomic Orbitals

Flashcards for Chemical Bonding II: Molecular Geometry and Hybridization of Atomic Orbitals. These flashcards are designed to help you review key concepts and vocabulary related to molecular geometry, VSEPR theory, dipole moments, valence bond theory, and molecular orbital theory.

Valence-Shell Electron-Pair Repulsion (VSEPR) Model

A model used to predict the shapes and bond angles in a molecule, based on the principle that electron groups around the central atom are most stable when they are as far apart as possible due to electron-pair repulsions.

Linear Geometry

Molecular geometry where the arrangement of electron pairs is linear, resulting in a straight line shape with a 180° bond angle (AB2).

Trigonal Planar Geometry

Molecular geometry where the arrangement of electron pairs is trigonal planar, resulting in a flat, triangular shape with 120° bond angles (AB3).

Tetrahedral Geometry

Molecular geometry where the arrangement of electron pairs is tetrahedral, resulting in a three-dimensional shape with 109.5° bond angles (AB4).

Trigonal Bipyramidal Geometry

Molecular geometry where the arrangement of electron pairs is trigonal bipyramidal (AB5).

Octahedral Geometry

Molecular geometry where the arrangement of electron pairs is octahedral (AB6).

Effect of Lone Pairs

Lone pairs occupy more space on the central atom, leading to greater repulsive forces and smaller bonding pair – bonding pair angles than expected. Lone Pair – Lone Pair > Lone Pair – Bonding Pair > Bonding Pair – Bonding Pair

Bent (V-shape) Geometry

Molecular geometry that is a derivative of trigonal planar electron geometry, where the bond angle is less than 120° due to the presence of a lone pair (AB2E).

Trigonal Pyramidal Geometry

A molecular geometry derived from tetrahedral electron geometry when one bonding pair is replaced by a lone pair (AB3E).

See-Saw Geometry

Molecular geometry that results from a trigonal bipyramidal arrangement with one lone pair in an equatorial position (AB4E).

T-shaped Geometry

Molecular geometry derived from a trigonal bipyramidal arrangement with two lone pairs in equatorial positions (AB3E2).

Square Pyramidal Geometry

Molecular geometry derived from an octahedral arrangement with one lone pair (AB5E).

Square Planar Geometry

Molecular geometry derived from an octahedral arrangement with two lone pairs (AB4E2).

Polar Molecule

A molecule with polar bonds and an unsymmetrical shape, resulting in a net dipole moment. Nonbonding pairs affect molecular polarity, creating a strong pull in their direction.

Dipole Moment

A quantitative measure of the degree of charge separation in a molecule, calculated as m = Q x r, where Q is the charge and r is the distance between charges.

Valence Bond (VB) Theory

A theory that describes covalent bond formation as the sharing of electrons from overlapping atomic orbitals, retaining a picture of individual atoms taking part in the bond formation.

Molecular Orbital (MO) Theory

A theory that describes the formation of molecular orbitals from atomic orbitals, assuming that electrons are delocalized over the entire molecule.

Hybridization

The mixing of two or more atomic orbitals to form a new set of hybrid orbitals (e.g., sp, sp2, sp3, sp3d, sp3d2). Covalent bonds are formed by overlap of hybrid orbitals with atomic orbitals or other hybrid orbitals.

Sigma (σ) Bond

A covalent bond with electron density concentrated between the two atoms.

Pi (π) Bond

A covalent bond with electron density above and below the plane of nuclei.

Bonding Molecular Orbital (BMO)

A molecular orbital that has lower energy and greater stability than the atomic orbitals from which it was formed, resulting from constructive interference of wave functions.

Antibonding Molecular Orbital (ABMO)

A molecular orbital that has higher energy and lower stability than the atomic orbitals from which it was formed, resulting from destructive interference of wave functions. Most of the electron density outside of the nuclei.

Bond Order

A measure of the number of chemical bonds between a pair of atoms. Calculated as (# of Bonding Electrons - # of Antibonding Electrons) / 2.

Paramagnetic

A substance that is attracted to a magnetic field due to the presence of unpaired electrons in its molecular orbital diagram.

Diamagnetic

A substance that is not attracted to a magnetic field because all of its electrons are paired.