Chapter 7 - Molecular Shape and Bonding Theories

Isomers

Different compounds with the same molecular formula but a different arrangement of atoms

Flash Point

Temperature at which vapors of a liquid fuel can be ignited

Valence shell electron pair repulsion (VSEPR) model

Model that uses the number of electron domains around a central atom to predict the most stable shape occupied by the domain due to repulsion

Electron Domains

A charge cloud around a central atom that can be any of these: lone pairs, single unshared electrons, single bond, double bond, or triple bond

Electron Geometry

Shape determined by the number of electron domains

Molecular Geometries

3D shape of a molecule

Linear

An electron geometry associated with 2 electron domains

Trigonal Planar

An electron geometry associated with 3 electron domains

Bent

A molecular geometry associated with 3 electron domains with 1 lone pair, or 4 electron domains with 2 lone pairs

Tetrahedron

Symmetric 3D shape consisting of 4 equilateral triangular faces

Tetrahedral

An electron geometry associated with 4 electron domains

Trigonal Pyramidal

Molecular geometry associated with 4 electron domains with 1 lone pair; a 3 sided pyramid

Trigonal Bipyramid

An electron geometry associated with 5 electron domains consisting of 2 3-sided pyramids sharing a base

See-saw

A molecular geometry associated with 5 electron domains with 1 lone pair

T-shaped

A molecular geometry associated with 5 electron domains with 2 lone pairs

Octahedral

An electron geometry associated with 6 electron domains

Square Pyramidal

A molecular geometry associated with 6 electron domains with 1 lone pair

Square Planar

A molecular geometry associated with 6 electron domains with 2 lone pairs

Molecular Dipoles

Molecular with uneven electron distribution; polar molecule

Polar Molecule

A molecule with asymmetric electron distribution; molecular dipole

Nonpolar Molecule

Molecule with symmetric electron distribution; no dipole

Valence Bond (VB) theory

Theory that explains bonding by the overlap of atomic orbitals and hybridization of atomic orbitals

Coordinate Covalent Bonds

A covalent bond in which both shared electrons come from the same atom

Hybrid Orbitals

Mathematical combinations of the standard atomic orbitals that result in maximal overlap of orbitals in bonds

sp³ Hybrid Orbitals

Hybrid orbitals formed from 1 s orbital and 3 p orbitals; associated with tetrahedral electron geometry

Sigma Bond

A type of bond formed by head-to-head overlap of orbitals along the internuclear axis; found in all covalent bonds

sp² hybrid orbitals

Hybrid orbitals formed from 1 s orbitals and 2 p orbitals; associated with trigonal planar electron geometry

Pi bond

Bond formed by side-on overlap of unhybridized p orbitals above and below the internuclear axis; found in double and triple bonds

sp hybrid orbitals

Hybrid orbitals formed from 1 s orbital and 1 p orbital; associated with linear electron geometry

Conformations

Various shapes possible for larger molecules due to rotation around single bonds

Molecular orbital (MO) theory

Theory that explains bonding by the combination of atomic orbitals to form bonding molecular orbitals and antibonding molecular orbitals

Molecular Orbitals

A type of orbital resulting from the combination of atomic orbitals in a molecule

Constructive

Waves combine in phase to increase peaks and decrease troughs

Destructive interference

Waves combine out of phase to cancel peaks and troughs

Bonding Orbital

Lower energy molecular orbital resulting from the additive combination of atomic orbitals

Antibonding orbital

A higher energy molecular orbital resulting from the subtractive combination of atomic orbitals, designated by *

Molecular orbital (MO) diagram

Similar to an atomic orbital diagram; shows the relative energy levels and electron population of the molecular orbital; used to predict properties

Bond order

Measure of the stability of the molecule, calculated from the MO diagram

Paramagnetic

Weak attraction to a magnetic field; a property of substances with at least one unpaired electron

Diamagnetic

Very slight repulsion from a magnetic field; a property of substances with all paired electrons

Nonbonding orbitals

Orbitals occupied by lone pairs in MO diagrams