Chemical Bonding, Molecular Geometry, and Intermolecular Forces

Vocabulary practice flashcards covering chemical bonding concepts, VSEPR and molecular geometry, valence bond and hybridization models, molecular orbital theory, and intermolecular forces from Chapters 4, 5, and 6.

Valence-Shell Electron-Pair Repulsion (VSEPR) Theory

A model that predicts the three-dimensional geometry of a molecule by arranging valence electron pairs around a central atom to minimize electrostatic repulsions and yield the lowest-energy configuration.

Electron-Pair Geometry

The three-dimensional spatial arrangement of all electron pairs—including both bonding pairs and lone pairs—surrounding a central atom.

Molecular Geometry

The three-dimensional arrangement of the bonded atoms in a molecule or polyatomic ion, defined exclusively by the positions of the atomic nuclei.

Bond Angle

The angle, measured in degrees, defined by the imaginary lines joining the nuclei of two surrounding atoms to the nucleus of the central atom to which they are bonded.

Bond Dipole

The separation of electrical charge along a covalent bond that occurs when two bonded atoms possess differing electronegativity values.

Dipole Moment ($\mu$)

A quantitative measure of the degree to which a polar molecule aligns itself in an applied electric field, expressed in units of debyes ($\text{D}$).

Valence Bond Theory

A quantum chemical bonding model that describes covalent bond formation as the spatial overlap of two atomic or hybridized orbitals, each containing an electron with paired spins.

Sigma ($\sigma$) Bond

A covalent bond formed by the direct, head-to-head overlap of atomic or hybrid orbitals along the internuclear axis between two nuclei.

Pi ($\pi$) Bond

A covalent bond formed by the sideways, parallel overlap of unhybridized $p$ orbitals in regions located above and below the internuclear axis.

Hybrid Orbitals

Equivalent atomic orbitals of distinct directional orientation and intermediate energy formed mathematically by mixing two or more non-equivalent atomic orbitals on the same atom.

Delocalization

The spatial extension of pi-bonding electrons over several adjacent atoms within a molecule or polyatomic ion, rather than being confined between two specific bonded nuclei.

Chirality

The geometric characteristic of a molecule or object that is non-superimposable on its mirror image.

Enantiomers

A pair of chiral stereoisomers related as non-superimposable mirror images of one another.

Molecular Orbital (MO) Theory

A bonding model describing the formation of delocalized molecular orbitals through the linear combination of atomic orbitals across the entire molecule.

Bonding Molecular Orbital

A molecular orbital characterized by high electron density between bonded nuclei that is lower in energy and more stable than the atomic orbitals from which it was formed.

Antibonding Molecular Orbital

A molecular orbital designated by an asterisk ($^*$) that features a nodal plane of zero electron density between nuclei, possessing higher energy and destabilizing the molecule relative to isolated atomic orbitals.

Bond Order

A quantitative indicator of covalent bond stability defined by the formula: $\text{Bond Order} = \frac{1}{2} [(\text{number of bonding } e^-) - (\text{number of antibonding } e^-)]$.

Paramagnetism

The physical property of a substance containing one or more unpaired electrons that results in its net attraction into an external magnetic field.

Diamagnetism

The physical property of a substance in which all electrons are paired, leading to a very weak repulsion away from an external magnetic field.

Intramolecular Forces

Attractive forces that hold atoms together within a discrete chemical entity or formula unit (such as covalent, ionic, and metallic bonds), the breaking of which alters chemical identity.

Intermolecular Forces

Non-covalent electrostatic attractions that occur between separate molecules, dictating physical properties such as boiling point, melting point, and viscosity without altering chemical composition.

London Dispersion Forces

Weak, transient intermolecular attractions present in all atoms and molecules that arise from temporary fluctuations in electron distribution creating instantaneous and induced dipoles.

Polarizability

The susceptibility of the electron cloud of an atom or molecule to being distorted or shifted out of shape by an external electrical field or nearby charge.

Viscosity

A physical measurement of a liquid's internal resistance to flow, which increases with larger molecular mass, longer carbon chains, and stronger intermolecular forces.

Functional Group

A specific atom or group of bonded atoms within an organic molecule that confers characteristic physical behavior and chemical reactivity.

Carbonyl Group

An organic functional group comprising a carbon atom double-bonded to an oxygen atom ($\text{C}=\text{O}$).

Ketone

An organic compound featuring a carbonyl group whose central carbon atom is bonded directly to two other carbon atoms.

Hydroxyl Group

A functional group consisting of an oxygen atom linked by a single covalent bond to a hydrogen atom ($-\text{OH}$).

Alcohol

An organic compound whose structure contains a hydroxyl group ($-\text{OH}$) attached to a carbon atom that is not bonded to other functional groups.

Ether

An organic compound containing a divalent oxygen atom covalently linked by single bonds to two distinct carbon atoms ($\text{R}-\text{O}-\text{R}'$).

Dipole-Dipole Interaction

An electrostatic attraction occurring between the permanent partial positive ($\delta^+$) pole of one polar molecule and the permanent partial negative ($\delta^-$) pole of a neighboring polar molecule.

Hydrogen Bond

A particularly strong class of dipole-dipole interaction occurring between a hydrogen atom covalently bonded to a highly electronegative atom ($\text{N}$, $\text{O}$, or $\text{F}$) and an unshared lone pair on a nearby $\text{N}$, $\text{O}$, or $\text{F}$ atom.

Sphere of Hydration

A concentric sheath of structured water molecules surrounding a dissolved ion in aqueous solution, stabilized by ion-dipole attractions.

Solubility

The maximum quantity of solute that can dissolve within a specified volume or mass of a solvent at a defined temperature and pressure.

Triple Point

The invariant temperature and pressure condition on a phase diagram at which solid, liquid, and gaseous phases of a substance coexist simultaneously in thermodynamic equilibrium.

Critical Point

The terminal temperature and pressure coordinates on a liquid-gas vapor pressure curve beyond which the physical boundary between liquid and gas ceases to exist.

Supercritical Fluid

A state of matter produced when temperature and pressure exceed the critical point values, displaying liquid-like density combined with gas-like cavity-penetrating ability.

Surface Tension

The energy required to expand the surface area of a liquid by a unit amount, resulting from unbalanced net inward cohesive intermolecular forces experienced by surface molecules.

Cohesive Forces

Intermolecular attractive forces that act between mutually identical molecules of the same liquid or solid substance.

Adhesive Forces

Intermolecular attractive forces exerted between unlike substances, such as molecules of a liquid and the surface atoms of a solid container.

Capillary Action

The spontaneous ascension or movement of a liquid within a narrow bore or porous medium against gravity, governed by the combined action of cohesive and adhesive forces.

Electronegativity ($\chi$)

A relative scale measuring the intrinsic ability of an atom participating in a chemical bond to attract shared electron pairs toward its own nucleus.

Ionic Bond

A chemical bond resulting from the non-directional electrostatic attraction between oppositely charged cations and anions formed by the complete transfer of valence electrons.

Crystal Lattice

A highly ordered, periodic three-dimensional geometric array of particles (atoms, ions, or molecules) composing a crystalline solid.

Lattice Energy ($U$)

The quantity of energy released when one mole of an ionic solid forms from its isolated gaseous constituent ions.

Covalent Bond

A chemical bond established between atoms through the mutual sharing of one or more pairs of valence electrons.

Polar Covalent Bond

A covalent linkage characterized by unequal electron pair sharing due to an electronegativity difference between $0.4$ and $2.0$, generating fractional partial charges ($\delta^+$ and $\delta^-$).

Metallic Bond

A chemical bonding interaction in metals wherein fixed, positive metallic atomic cores are held together by a shared, highly mobile, delocalized electron cloud.

Polyatomic Ion

An aggregate of two or more covalently bonded atoms carrying a net positive or negative electrical charge.

Oxoanion

A polyatomic anion comprising one or more oxygen atoms bonded covalently to another nonmetal or metalloid element.

Octet Rule

The empirical guideline stating that main-group elements tend to react by losing, gaining, or sharing electrons until their valence shells contain eight electrons, achieving a noble-gas valence electron configuration.

Bonding Capacity

The characteristic number of covalent bonds an atom of a particular element typically forms to complete its valence shell octet.

Bond Length

The internuclear distance between two covalently bonded atoms at the position of minimum potential energy.

Bond Energy

The amount of energy required to homolytically dissociate one mole of specific covalent bonds in the gas phase.

Resonance Structures

Two or more legitimate Lewis representations for a chemical entity exhibiting identical nuclear skeletal arrangements but alternate configurations of shared electron pairs and lone pairs.

Formal Charge

A fictitious bookkeeping charge assigned to an atom in a Lewis formula, calculated by: $\text{FC} = (\text{valence } e^-) - [(\text{lone pair } e^-) + \frac{1}{2}(\text{bonding } e^-)]$.

Free Radical

An uncharged or charged molecular species possessing an odd number of valence electrons, resulting in an unpaired electron and marked chemical reactivity.

Expanded Octet

A hypervalent condition in which a central nonmetal atom from period 3 or below is surrounded by more than eight valence electrons, typically when bonded to strongly electronegative ligands.