Comprehensive Guide to Chemical Bonding and Molecular Geometry

Chemical bonds

Attractive forces that hold atoms together.

Intramolecular forces

Forces affecting the structure within a single molecule or ionic lattice.

Electronegativity

The tendency of an atom to attract bonding electrons.

Nonpolar Covalent Bond

A bond where electrons are shared equally, usually with $ ext{Δ} ext{𝜒}<0.4$.

Polar Covalent Bond

A bond where electrons are shared unequally, usually with $0.4< ext{Δ} ext{𝜒}<1.7$.

Ionic Bond

A bond formed when electrons are transferred completely from a metal to a nonmetal, usually $ ext{Δ ext{𝜒}>1.7}$.

Percent ionic character

A measure of the degree of ionic character in a bond.

Potential Energy Diagram

Graph that shows potential energy as a function of distance between atoms.

Bond Length

The distance at which the potential energy between two bonded atoms is minimized.

Covalent bond formation

Occurs at distances where attractive forces balance repulsive forces.

Ionic compounds

Compounds formed by the electrostatic attraction between cations and anions.

Crystal Lattice

A rigid structure formed by alternating positive and negative ions.

Conductivity of Ionic Solids

Ionic solids do not conduct electricity; liquids and dissolved ions do.

Lattice Energy

Energy released when ions form a stable crystal lattice.

Coulomb's Law

Describes the force between two charged particles: $F ext{propto}rac{Q1 Q2}{r^2}$.

Charge Magnitude

The significance of ionic charge in determining bond strength.

Ionic Radius

The size of an ion, affecting the strength of ionic bonds.

Metallic Bonding

Bonding that occurs when positive metal ions are surrounded by a sea of delocalized electrons.

Alloy

A mixture of metals.

Interstitial Alloy

Small atoms filling spaces between larger metal atoms.

Substitutional Alloy

Atoms of similar radius replace distinct metal atoms.

Lewis Structures

Diagrams representing the bonding between atoms in a molecule.

Formal Charge

A calculation to determine the charge on an atom in a molecule.

Resonance

A phenomenon where more than one valid Lewis structure can be drawn for a molecule.

Octet Rule

Atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons.

Valence Shell Electron Pair Repulsion (VSEPR) theory

Theory predicting molecular geometry based on electron pair repulsion.

Repulsion Hierarchy

Order of strength of repulsive forces between electron domains.

Molecular Geometry

The three-dimensional arrangement of atoms in a molecule.

Bond Hybridization

The mixing of atomic orbitals to form new hybrid orbitals.

Sigma Bond ($$)

A bond formed by head-to-head overlap of orbitals.

Pi Bond ($$)

A bond formed by side-to-side overlap of unhybridized p-orbitals.

Bond Counting

A method to classify the type of bonds in a molecule.

Ionic Properties

Characteristics of ionic compounds including high melting points and low volatility.

Covalent Properties

Characteristics of covalent compounds including lower melting points and volatility.

Metallic Properties

Properties of metals such as conductivity and malleability.

Network Covalent Properties

Very high melting points and non-conductivity except for graphite.

Common Mistake: Bond Polarity vs Molecular Polarity

A molecule can have polar bonds but be nonpolar if symmetrical.

Lattice Energy Logic

Melting point explanations should mention Coulomb's Law and charge magnitude.

Lewis Structures: Total Valence Count

Always include charges of polyatomic ions when counting valence electrons.

Bond Angles in Bent Molecules

Lone pairs can decrease bond angles, e.g., $H_2O$.

Expanded Octet

Ability of Period 3 or higher elements to hold more than 8 electrons.

Incomplete Octet

Some elements, like Boron, can be stable with fewer than 8 electrons.